Magnetoresistance effect element, its manufacturing method, magnetic reproducing element and magnetic memory

ABSTRACT

A magnetoresistance effect element includes a first ferromagnetic layer ( 1 ), insulating layer ( 3 ) overlying the first ferromagnetic layer, and second ferromagnetic layer ( 2 ) overlying the insulating layer. The insulating layer has formed a through hole (A) having an opening width not larger than 20 nm, and the first and second ferromagnetic layers are connected to each other via the through hole.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of application Ser. No. 10/244,550filed on Sep. 17, 2,002 Now U.S. Pat. No. 6,937,447.

This application is based upon and claims the benefit of priority fromthe prior Japanese Patent Application No. 2001-284467, filed on Sep. 19,2001; the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

This invention relates to a magnetoresistance effect (MR) element, itsmanufacturing method, and its use as a magnetic recording element or amagnetic memory. More particularly, the invention relates to amagnetoresistance effect element having magnetic nanocontacts thatexhibit high magnetoresistance ratios, its manufacturing method, and itsuse as a magnetic reproducing element or a magnetic memory.

Since the discovery that a giant magnetoresistance effect occurs when acurrent is supplied to flow in parallel with the major plane of amulti-layered structure, efforts have been made to find systems havingstill larger magnetoresistance ratios. Thus, ferromagnetic tunneljunction elements and CPP (current perpendicular to plane) type MRelements in which electric current flows vertically in a multi-layeredstructure have been developed and suggested for use as magnetic sensorsand reproducing elements for magnetic recording.

In the technical field of magnetic recording, enhancement of therecording density inevitably requires miniaturization of the recordingbit, and this makes it more and more difficult to ensure sufficientsignal intensity. Accordingly, materials exhibiting an even moresensitive magnetoresistance effect are in demanded, and the importanceof systems having large magnetoresistance ratios, as referred to above,is greater and greater.

Recently, “magnetic nanocontacts” by tip-to-tip abutment of two nickel(Ni) needles and nanocontacts by contact of two magnetite elements havebeen reported as elements exhibiting 100% or higher magnetoresistiveeffects, see (1) Garcia, M. Munoz and Y.-W. Zhao, Physical ReviewLetters, vol.82, p2923 (1999) and (2) J. J. Versluijs, M. A. Bari and J.W. D. Coery, Physical Review Letters, vol. 87, p 26601-1 (2001),respectively. These nanocontacts certainly exhibit largemagnetoresistive changes. In both proposals, however, the magneticnanocontacts are made by bringing two needle-shaped or triangular-shapedferromagnetic elements into tip-to-tip contact.

More recently, magnetic nanocontacts have been formed by arranging twothin nickel wires in a “T”-configuration and by growing a micro columnat the connecting point thereof by electroplating technique, see (3) N.Garcia et. al., Appl. Phys. Lett., vol.80, p1785 (2002) and (4) H. D.Chopra and S. Z. Hua, Phys. Rev. B, vol.66, p.20403-1 (2002).

These magnetic nanocontacts also exhibit a large mangetoresistancechange, however, the strucutre of these magnetic nanocontacts makes italmost impossible to realize a practical magnetoresistance effectelement.

Another group has reported a magnetic nanocontact which was formed bygrowing a cluster of nickel using an electroplating technique in apinthrough hole made on an alumina layer, see (5) M. Munoz, G. G. Qian,N. Karar, H. Cheng, I. G. Saveliev, N. Garcia, T. P. Moffat, P. J. Chen,L. Gan, and W. F. Egelhoff, Jr., Appl. Phys. Lett., vol.79, p.2946,(2001).

However, it is difficult to control the magnetic domain structure andthe configuration of the point contact, therefore, the resultingmagnetoresistance ratio is as small as 14% or even smaller.

Magnetic nanocontacts have a potential to exhibit a largemagnetoresistance ratio, however, in order to ensure a largemagnetoresistive effect therewith, the structures proposed by theabove-noted articles include placing two needle-shaped ferromagneticelements in tip-to-tip abutment or growing a micro column between twowires by an electroplating technique, and this and other requirementsmake it difficult to accurately control the contact portions in themanufacturing process. Taking into account of the application of suchmagnetic nanocontacts to magnetic heads or solid magnetic memorydevices, however, it is necessary to develop a structure fornanocontacts that is suitable for mass production under reasonablecontrol, as well as the manufacturing method to achieve such astructure. Additionally, to detect the difference in magnetizationdirections on opposite sides of a nanocontact, control of magneticdomains of both magnetic electrodes is important. Therefore, in order torealize a practical magnetoresistance effect element, it is essential todevelop a structure where the control of the magnetic domains of theboth magnetic electrodes is quite easy.

SUMMARY OF THE INVENTION

According to the present invention, there is provided amagnetoresistance effect element comprising: a first ferromagneticlayer; an insulating layer overlying said first ferromagnetic layer; anda second ferromagnetic layer overlying said insulating layer, saidinsulating layer having a through hole penetrating its thicknessdirection at a predetermined position, said first ferromagnetic layerand said second ferromagnetic layer being electrically connected to eachother via said through hole, and said through hole having an openingwidth not larger than 20 nm.

According to another embodiment of the invention, there is provided amagnetic reproducing element comprising a magnetoresistance effectelement including: a first ferromagnetic layer; an insulating layeroverlying said first ferromagnetic layer; and a second ferromagneticlayer overlying said insulating layer, said insulating layer having athrough hole penetrating its thickness direction at a predeterminedposition, said first ferromagnetic layer and said second ferromagneticlayer being electrically connected to each other via said through hole,and said through hole having an opening width not larger than 20 nm,said magnetoresistance effect element being provided on a path of themagnetic flux emitted from a magnetic recording medium so that saidfirst and second ferromagnetic layers are serially aligned on a path ofthe magnetic flux emitted from a magnetic recording medium, and saidmagnetoresistance effect element detects a difference betweenmagnetization directions of said first and second ferromagnetic layersas a resistance change.

According to an embodiment of the present invention, there is provided amagnetic reproducing element comprising a magnetoresistance effectelement including: a first ferromagnetic layer; an insulating layeroverlying said first ferromagnetic layer; and a second ferromagneticlayer overlying said insulating layer, said insulating layer having athrough hole penetrating its thickness direction at a predeterminedposition, said first ferromagnetic layer and said second ferromagneticlayer being electrically connected to each other via said through hole,and said through hole having an opening width not larger than 20 nm, andsaid magnetoresistance effect being arranged so as to make a main planeof said first ferromagnetic layer substantially perpendicular to arecording surface of said magnetic recording medium.

According to yet another embodiment of the present invention, there isprovided a magnetic memory comprising: magnetoresistance effect elementincluding: a first ferromagnetic layer being pinned in magnetization ina first direction; an insulating layer overlying said firstferromagnetic layer; a second ferromagnetic layer overlying saidinsulating layer, said second ferromagnetic layer being free indirection of magnetization, and at least one of a reading and a writingbeing executable by flowing a current in a direction of its layerthickness; a nonmagnetic intermediate layer overlying said secondferromagnetic layer; and a third ferromagnetic layer overlying saidnonmagnetic intermediate layer and being pinned in magnetization in asecond direction substantially opposite from said first direction, saidinsulating layer having a through hole penetrating its thicknessdirection at it's a predetermined position, said first ferromagneticlayer and said second ferromagnetic layer being electrically connectedto each other via said through hole, and said through hole having anopening width not larger than 20 nm.

According to yet another embodiment of the present invention, there isprovided a magnetic memory comprising: magnetoresistance effect elementincluding: a first ferromagnetic layer being pinned in magnetization ina first direction; an insulating layer overlying said firstferromagnetic layer; a second ferromagnetic layer overlying saidinsulating layer, said second ferromagnetic layer being free indirection of magnetization, and at least one of a reading and a writingbeing executable by flowing a current in a direction of its layerthickness; a nonmagnetic intermediate layer overlying said secondferromagnetic layer; and a third ferromagnetic layer overlying saidnonmagnetic intermediate layer and being pinned in magnetization in saidfirst direction, said insulating layer having a through hole penetratingits thickness direction at its a predetermined position, said firstferromagnetic layer and said second ferromagnetic layer beingelectrically connected to each other via said through hole, and saidthrough hole having an opening width not larger than 20 nm.

According to yet another embodiment of the invention, there is provideda magnetic memory comprising a magnetoresistance effect elementincluding: a first ferromagnetic layer; an insulating layer overlyingsaid first ferromagnetic layer; and a second ferromagnetic layeroverlying said insulating layer, said insulating layer having a throughhole penetrating its thickness direction at it's a predeterminedposition, said first ferromagnetic layer and said second ferromagneticlayer being electrically connected to each other via said through hole,and said through hole having an opening width not larger than 20 nm, oneof said first and second ferromagnetic layers being pinned inmagnetization in a first direction, another of said first and secondferromagnetic layers being free in direction of magnetization and atleast one of reading and writing being executable by flowing a currentin a direction of thicknesses of said first and second ferromagneticlayers.

According to yet another embodiment of the present invention, there isprovided a magnetic memory comprising a plurality of memory cells, saidmemory cells being two-dimensionally arranged, each of said memory cellsbeing separated each other by insulating region, a current beingprovided to each of said memory cells by a conductive probe or fixedwiring, an absolute value of a writing current provided to each of saidmemory cells being larger than an absolute value of a reading currentprovided to each of said memory cells, and each of said memory cellshaving a magnetoresistance effect element including: a firstferromagnetic layer; an insulating layer overlying said firstferromagnetic layer; and a second ferromagnetic layer overlying saidinsulating layer, said insulating layer having a through holepenetrating its thickness direction at it's a predetermined position,said first ferromagnetic layer and said second ferromagnetic layer beingelectrically connected to each other via said through hole, and saidthrough hole having an opening width not larger than 20 nm, one of saidfirst and second ferromagnetic layers being pinned in magnetization in afirst direction, and the other of said first and second ferromagneticlayers being free in direction of magnetization and said writing currentand said reading current being provided in a direction of thicknesses ofsaid first and second ferromagnetic layers.

In this specification, “magnetoresistance ratio” is defined to be achange in electrical resistance divided by electrical resistance. Thatis, the magnetoresistance ratio is obtained by dividing a change inelectrical resistance by the electrical resistance at the magneticfield. In the case where the magnetization is unsaturated under theinsufficient magnetic field, the magnetoresistance ratio is obtained bydividing the electrical resistance change by the smallest resistance ofthe MR element.

Also in this specification, “resistance between a first ferromagneticlayer and a second ferromagnetic layer” is defined as an average. Thatis, let the maximum resistance between the first and secondferromagnetic layers be Rmax, and the minimum resistance therebetween beRmin, “resistance between a first ferromagnetic layer and a secondferromagnetic layer” is defined as the average of these values whichequals to (Rmax+Rmin)/2.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be understood more fully from the detaileddescription given herebelow and from the accompanying drawings of theembodiments of the invention. However, the drawings are not intended toimply the limitation of the invention to a specific embodiment, but arefor explanation and understanding only.

IN THE DRAWINGS

FIGS. 1A and 1B are diagrams that roughly illustrate cross-sectionalstructures of substantial parts of magnetoresistance effect elementsaccording to an embodiment of the invention;

FIGS. 2A through 2D are schematic diagrams for explaining a relationbetween an applied magnetic field and the electric resistance;

FIGS. 3A and 3B are schematic diagrams for explaining changes ofmagnetoresistance by a typical anisotropic magnetoresistive effect;

FIGS. 4A through 4F are diagrams that roughly show properties ofmagnetoresistance effect elements according to an embodiment of theinvention in comparison with properties of conventionalmagnetoresistance effect elements;

FIGS. 5A through 5D are diagrams that roughly illustratemagnetoresistance effect elements having a plurality of nanocontacts;

FIGS. 6A through 6C are diagrams roughly illustrating cross-sectionalforms of openings of nanocontacts;

FIGS. 7A and 7B are diagrams that roughly illustrate magnetoresistanceeffect elements each locating a region D added with a different kind ofelement near the opening end of a nanocontact A;

FIGS. 8A through 8D are cross-sectional views of the substantial part ofa magnetoresistance effect element according to an embodiment of theinvention under a manufacturing process;

FIG. 9 is a cross-sectional view of a structure having an arrangement ofa plurality of magnetoresistance effect elements on a common substrate(not shown);

FIGS. 10A through 10C are diagrams that roughly show specific examplesusing magnetoresistance effect elements according to an embodiment ofthe invention as magnetic reproducing elements;

FIGS. 11A through 11C are diagrams that roughly show other specificexamples using magnetoresistance effect elements according to anembodiment of the invention that monitor resistance ΔR;

FIG. 12 is a schematic diagram roughly illustrating a cross-sectionalstructure of the substantial part of a magnetic memory device usingmagnetoresistance effect elements according to an embodiment of theinvention;

FIGS. 13A through 13B are diagrams roughly illustrating access means toindividual recording/reproducing cells 10;

FIGS. 14A through 14D are diagrams that roughly show cross-sectionalstructures of magnetoresistance effect elements 10 that are used in themagnetic memory device of FIG. 12;

FIGS. 15A through 15H are diagrams roughly showing cross-sectionalstructures of magnetoresistance effect elements 10 that are used in themagnetic memory device of FIG. 12;

FIGS. 16A through 16E are cross-sectional views that roughly show otherspecific examples of magnetoresistance effect element usable in themagnetic memory device of FIG. 12;

FIGS. 17A and 17B are graph diagrams that show changes in distancebetween the top surface of a ferromagnetic layer 1 and the tip portionof a needle 110 and changes in current flowing between them,respectively, with time, when the needle 110 is thrust at a constantspeed;

FIG. 18 is a graph diagram showing a relation between applied magneticfield and electrical resistance in a magnetoresistance effect elementaccording to an embodiment of the invention;

FIGS. 19A and 9B are diagrams roughly showing a cross-sectionalstructure of a substantial part of a agnetoresistance effect elementexperimentally prepared as the fourth example of the invention;

FIG. 20 is a diagram roughly showing a cross-sectional structure of asubstantial part of a magnetoresistance effect element experimentallyprepared in an embodiment of the invention;

FIG. 21 is a diagram roughly showing a cross-sectional structure of asubstantial part of a magnetoresistance effect element prepared in anexample of the invention;

FIG. 22 is a graph diagram showing changes of magnetoresistance of amagnetoresistance effect element according to an example of theinvention;

FIG. 23 is a diagram roughly showing a cross-sectional structure of anelement formed in the seventh example of the invention, viewed from amedium 200;

FIG. 24 is a diagram roughly showing an array connection of a pluralityof probes via transistors TR;

FIGS. 25A through 25C are diagrams roughly showing plan-viewedconfigurations of a SiO₂ layer 3 that changes with growth time;

FIG. 26 is a graph diagram showing growth time of a SiO₂ layer on theabscissa and MR ratio on the ordinate;

FIG. 27 is a diagram roughly illustrating a method used in the tenthexample of the invention;

FIG. 28 is a diagram roughly showing a process of fabricating amagnetoresistance effect element;

FIGS. 29A and 29B are diagrams roughly showing an example of forming aNb film 400;

FIGS. 30A through 30C are cross-sectional views roughly showing aprocess of forming a nanocontact;

FIGS. 31A through 31C are cross-sectional views roughly showingcontinuous part of the process shown in FIGS. 30A through 30C;

FIGS. 32A through 32C are cross-sectional views roughly showing anotherprocess of forming a nanocontact;

FIG. 33 is a diagram roughly showing an aspect of milling with obliqueangle of incidence;

FIGS. 34A through 34C are cross-sectional views roughly showing amanufacturing process of a magnetoresistance effect element taken as anexample of the invention;

FIGS. 35A through 35C are cross-sectional views roughly showing amanufacturing process of a magnetoresistance effect element taken asanother example of the invention;

FIGS. 36A through 36C are cross-sectional views roughly showing amanufacturing process of a magnetoresistance effect element taken asanother example of the invention;

FIGS. 37A through 37C are cross-sectional views roughly showing amanufacturing process of a magnetoresistance effect element taken asanother example of the invention;

FIGS. 38A through 38C are diagrams roughly showing different results ofspot irradiation of electron beams;

FIG. 39 is a diagram roughly illustrating the position for EBirradiation relative to the device center C;

FIG. 40 is a diagram that roughly illustrates configuration of a device;

FIGS. 41A and 41B are diagrams that roughly show a process of localannealing;

FIG. 42 is a diagram roughly illustrating an MR element having somegrowth axes;

FIGS. 43A and 43B are diagrams roughly showing a process of uniformingorientation of crystal grains;

FIGS. 44A and 44B are cross-sectional views roughly showing an annealingprocess inserted in the film-stacking process;

FIGS. 45A and 45B are cross-sectional views roughly showing an annealingprocess executed after the film-stacking process;

FIGS. 46A through 46C are cross-sectional views roughly showing aprocess of removing damage produced in the boring process;

FIGS. 47A and 47B are cross-sectional views roughly illustrating amethod of making micro through holes;

FIGS. 48A and 48B are cross-sectional views roughly showing a method ofpreventing over-etching;

FIGS. 49A through 49C are cross-sectional views roughly showing aprocess of making a micro through hole by sequentially using differentways of etching;

FIGS. 50A through 50C are cross-sectional views roughly showing atechnique for minimizing unintended removal of the insulting layer;

FIGS. 51A through 51C are cross-sectional views roughly showing atechnique using FIB;

FIG. 52 is a diagram roughly showing a model using a spacer layer;

FIGS. 53A through 54D are diagrams roughly showing a process taken as afurther example;

FIG. 55 is a schematic diagram for explaining a process using a reducingreaction, taken as a further example;

FIG. 56 is a diagram roughly showing an alternative of the process shownin FIG. 55;

FIG. 57 is a diagram roughly showing another process using reduction;

FIGS. 58A and 58B are rough diagrams for explaining a process usingoxidation;

FIG. 59A is a diagram roughly showing a structure including a spacerlayer to explain functions of the spacer layer;

FIG. 59B is a diagram roughly showing an aspect of the spacer layerpartly removed by etching;

FIG. 59C is a diagram roughly showing an aspect of the spacer layerpartly removed by etching;

FIGS. 60A and 60B are diagrams roughly showing an aspect of the upperspacer layer 4 and the upper magnetic layer 2 stacked;

FIGS. 61A through 61C are diagrams roughly showing a process of buryingthe contact through hole with a magnetic material;

FIG. 62 is a diagram roughly showing a magnetoresistance effect elementin which electricity is applied in parallel to the film plane;

FIGS. 63A through 63D are diagrams roughly illustrating a process offabricating the magnetoresistance effect element shown in FIG. 62;

FIG. 64 is a diagram roughly showing a rounded shape of the magneticlayer in relation with the beam profile;

FIG. 65 is a diagram roughly showing a process using a protective filmPF;

FIG. 66 is a diagram roughly showing a process additionally using aphoto resist; and

FIG. 67 is a diagram roughly showing a process capable of substantiallynarrowing a contact.

DETAILED DESCRIPTION

Some embodiments of the invention will now be explained below withreference to the drawings.

FIGS. 1A and 1B are schematic diagrams that illustrate cross-sectionalstructures of substantial parts of magnetoresistance effect elementsaccording to an embodiment of the invention.

In the magnetoresistance effect element according to this embodiment, aninsulating layer 3 having a micro through hole A is formed on a firstferromagnetic layer 1, either directly or indirectly, on a substrate S,and a second ferromagnetic layer 2 is formed to bury the micro throughhole A.

The width of the micro through hole A opening is preferably not largerthan 20 nm at the narrowest portion as explained later in greaterdetail. If the opening shape of the micro through hole A is circular,the “opening width” means its diameter. If the opening shape ispolygonal, it means the longest of its diagonals. If it has an isometricshape, such as a flat circle, it means the longest of its openingwidths.

The insulating layer 3 has a through hole of a conical, circular,pyramidal, columnar or prismatic shape, or any other appropriate shape,toward the first ferromagnetic layer 1, and a part of the through hole Aforms the micro through hole A. In one of the preferred embodiments ofthe invention, the micro through hole A is located near the firstferromagnetic layer.

That is, the magnetoresistance effect element shown here has a magneticnanocontact that brings the first ferromagnetic layer 1 and the secondferromagnetic layer 2 into contact at the micro through hole A.

Further, the ferromagnetic layers 1, 2 function as electrodes, orelectrodes are provided separately and connected to them. The electricresistance obtained between the ferromagnetic layers 1, 2 by applicationof a current between the electrodes changes with regard to the relativemagnetization arrangement.

That is, when the opening width of the magnetic nanocontact formed atthe micro through hole A decreases to 20 nm or less, the through holefunctions as a generating point of an ultra-thin magnetic wall. Then,the relative magnetic arrangement between the ferromagnetic layers 1 and2 can be changed by applying an external magnetic field to either one ofthe ferromagnetic layers 1 and 2, and this change cause a change in theelectric resistance between the first and second ferromagnetic layers 1and 2.

Relative to the magnetoresistance effect element shown here, theelectric resistance basically decreases with the magnetic field in bothmagnetic directions over a certain magnetic field range. Therefore, themagnetoresistive effect generated here can be regarded to be amagnetoresistive effect generated by the magnetic wall formed by thenanocontact. This magnetic wall functions as a transition region betweentwo portions having a different magnetization direction relative to eachother. In this magnetoresistance effect element, a magnetoresistiveeffect as large as 20% or more is generated depending on the magnitudeof the applied magnetic field.

FIGS. 2A through 2D are schematic diagrams for explaining a relationbetween an applied magnetic field and the electric resistance. FIGS. 2Aand 2C are graph diagrams that demonstrate changes of electricresistance obtained by applying a magnetic field in parallel to the filmplane of the ferromagnetic layer 1 or 2 when the opening width of themicro through hole A, i.e. magnetic nanocontact, is 20 nm or less.Similarly, FIGS. 2B and 2D are graph diagrams that demonstrate changesof electric resistance obtained by applying a magnetic fieldperpendicularly to the film plane of the ferromagnetic layer 1 or 2 whenthe opening width of the micro through hole A is 20 nm or less. FIGS. 2Athrough 2D are shown for the most simple basic structure which does notinclude an exchange bias film. Also these figures show the case wherethe easy axis of magnetization of the element lies in parallel to thefilm plane.

As apparent from these graph diagrams, when the opening width of themicro through hole A is 20 nm or less, in a certain range of themagnetic field, electric resistance basically decreases with the appliedmagnetic field irrespectively of the direction of the magnetic field.When the magnetic field is applied in a direction of a hard axis ofmagnetization, the resistance decrease may not be as clear because thechange is very small.

When the opening width of the magnetic nanocontact becomes larger than20 nm, the ordinary anisotropic magnetoresistance effect becomesnoticeable. That is, electric resistance varies in accordance with thedirection of the magnetic field applied.

FIGS. 3A and 3B are schematic diagrams for explaining changes ofmagnetoresistance by such a typical anisotropic magnetoresistive effect.In the case of such an anisotropic magnetoresistance effect, if themagnetic field is applied perpendicularly relative to the current, thatis, in parallel to the film plane of the ferromagnetic layer 1 or 2,electric resistance slightly decreases due to application of themagnetic field as shown in FIG. 3A.

On the other hand, if the magnetic field is applied in parallel to thecurrent, i.e. perpendicular to the film plane of the ferromagnetic layer1 or 2, magnetization is not easily saturated with respect to themagnetic field, and as shown in FIG. 3B, although the gradient of themagnetic field is small, electric resistance rises in response toapplication of the magnetic field. However, as appreciated from FIGS. 3Aand 3B, when the element exhibits an ordinary anisotropicmagnetoresistive effect, the magnetoresistance ratio hits a peak atseveral %.

In contrast, in the magnetoresistance effect element according to theembodiment of the invention, electric resistance changes greatly withregard to the magnetic field regardless of the direction of the magneticfield applied as shown in FIGS. 2A through 2D, and moreover, themagnetoresistance ratio is remarkably large.

The reason why the magnetoresistance effect element according to theinvention exhibits a larger magnetoresistance ratio than conventionalmagnetoresistance effect elements is explained below.

FIGS. 4A through 4F are diagrams that show properties ofmagnetoresistance effect elements according to the embodiment of theinvention in comparison with properties of conventionalmagnetoresistance effect elements.

FIGS. 4A through 4F contain schematic diagrams of elements together withindication of magnetization directions in upper parts, and correspondingpotential diagrams in lower parts. FIGS. 4A and 4B are those of CPP typemagnetoresistance effect elements, FIGS. 4C and 4D are those ofmagnetoresistance effect elements having nanocontacts according toembodiments of the invention, and FIGS. 4E and 4F are those ofmagnetoresistance effect elements not having nanocontacts, for parallelmagnetization arrangement and anti-parallel magnetization arrangement.

Using these schematic drawings, an explanation is presented below as toelectron flow from the ferromagnetic layer 1 to the ferromagnetic layer2.

In the case of the CPP-MR shown in FIGS. 4A and 4B, an intermediatelayer 40 between the ferromagnetic layers 1 and 2 is made of anonmagnetic material such as copper (Cu). That is, the CPP type MRelements each have a multi-layered structure of cobalt (Co)/copper(Cu)/cobalt (Co). In these CPP type MR elements, if directions ofmagnetization M are parallel between the ferromagnetic layer 1 and thatof the ferromagnetic layer 2, as shown in FIG. 4A, up-spin electronsflow from the ferromagnetic layer 1 via the intermediate layer 40 intothe ferromagnetic layer 2. If directions of magnetization M areanti-parallel between the ferromagnetic layers 1 and 2, as shown in FIG.4B, up-spin electrons having arrived without being scattered uponpassing the intermediate layer 40 from the ferromagnetic layer 1 movetoward the ferromagnetic layer 2 and are scattered in the ferromagneticlayer 2.

In the case of MR elements according to the embodiment of the invention,if directions of magnetization M are parallel as shown in FIG. 4C,up-spin electrons and downspin electrons directly flow from theferromagnetic layer to the ferromagnetic layer 2. If directions ofmagnetization M are anti-parallel as shown in FIG. 4D, a very thinmagnetic wall is formed at the portion of the nanocontact, anddirections of magnetization M rapidly change (in FIG. 4D, thickness ofthe magnetic wall is equivalent to thickness of the drawing line, forexample). Therefore, up-spin electrons are scattered in theferromagnetic layer 2, and downspin electrons are also scattered in theferromagnetic layer 2. As such, in the case of the MR element accordingto the embodiment, since both up-spin and down-spin electrons arescattered, a magnetoresistive effect larger than those of the CPP-MRelements shown in FIGS. 4A and 4B can be obtained.

As will be explained later in detail, the inventors have found that alarge magnetoresistance effect can also be obtained in the case where anadditive element is introduced into the connecting portion at thethrough hole. In this case, since the thickness of the layer where theadditive element is incorporated is very small, the existence of theadditive element can be neglected in the above-explained mechanism shownin FIGS. 4C and 4D.

On the other hand, if the nanocontact has a size exceeding 20 nm, ifdirections of magnetization M are anti-parallel, the magnetic wallbetween them becomes very thick, and makes it difficult for electrons tohold spin information even after passing therethrough. As a result, itbecomes difficult to obtain the magnetoresistive effect derived from thechange in direction of magnetization M.

This is the reason why the magnetoresistance effect element according tothe embodiment of the invention exhibits a very large magnetoresistanceratio.

In the embodiment of the invention, since a multi-layered structure isused as the element structure for easier control of magnetization M ofthe ferromagnetic layers 1, 2, the state of magnetization shown in FIG.4D can be easily realized.

Consequently, although the magnetoresistance effect element according tothe embodiment of the invention decreases in electric resistance uponapplication of a magnetic field, if any hysteresis exists, theresistance maximum may shift slightly from the zero magnetic field asshown in FIG. 2A. Alternatively, the resistance may drop when themagnetic field is around zero. In both cases, once the resistancemaximum is exceeded by applying the magnetic field, the electricresistance decreases until all directions of magnetization of theelement are aligned in parallel by further application of a magneticfield.

Turning back to FIGS. 1A and 1B, in the magnetoresistance effect elementaccording to this embodiment of the invention, the ferromagnetic layers1 and 2 sandwiching the nanocontact have a film-like plane for easiercontrol of the magnetic domain. In this manner, it is possible to makethe magnetization distribution profile uniform, thereby sharply keep thewidth of the magnetic wall between this and the other ferromagneticlayers connected at the nanocontact, and, accordingly, obtain a largemagnetoresistance ratio.

However, the ferromagnetic layer 1 and the insulating layer 3 need notbe a strictly flat layer, but may have small undulations or curves asshown in FIG. 1B.

Furthermore, in the embodiment of the invention, a plurality ofnanocontacts may be provided as shown in FIGS. 5A through 5D. When aplurality of nanocontacts are used, although the MR value decreases,“fluctuation” of MR value among elements can be reduced as compared withthe model having a single nanocontact, and stable MR characteristics canbe easily reproduced.

The opening configuration of each nanocontact may be bowl-shaped asshown in FIGS. 5A and 5B, or may define a spherical convex shape formedon the flat ferromagnetic layer 1 as shown in FIG. 6A. Alternatively, itmay be a vertical wall surface as shown in FIG. 6B. Alternatively, asshown in FIG. 6C, it may define spherical surfaces convex into bothferromagnetic surfaces 1 and 2.

The insulating layer 3 encircling the magnetic nanocontact may be madeof a polymer, or an oxide, nitride or fluoride containing at least oneelement among aluminum (Al), titanium (Ti), tantalum (Ta), cobalt (Co),nickel (Ni), silicon (Si), iron (Fe), zirconium (Zr) and hafnium (Hf).Alternatively, the insulating layer 3 may be made of a compoundsemiconductor having a high resistance such as aluminum arsenide (AlAs).

The ferromagnetic layers 1, 2 may be made of a soft-magnetic materialsuch as an element among iron (Fe), cobalt (Co), nickel (Ni), etc., analloy containing at least one element among iron (Fe), cobalt (Co),nickel (Ni), manganese (Mn) and chromium (Cr), a NiZr-family alloycalled “Permalloy”, a CoNbZr-family alloy, a FeTaC-family alloy, aCoTaZr-family alloy, a FeAlSi-family alloy, a FeB-family alloy, aCoFeB-family alloy, or the like, or a half-metal magnetic material suchas a Heusler alloy, CrO₂, Fe₃O₄, or La_(1-x) Sr_(x) MnO₃. Alternatively,the ferromagnetic layers 1, 2 may be made of a compound semiconductor oroxide semiconductor containing at least one magnetic element among iron(Fe), cobalt (Co), nickel (Ni), manganese (Mn) and chromium (Cr), suchas (Ga, Cr)N, (Ga, Mn)N, MnAs, CrAs, (Ga, Cr)As, Zn O:Fe, (Mg, Fe). Anyof these materials having a magnetic property suitable for the intendeduse and may be selected.

The ferromagnetic layer 1 and 2 may be made of a single film, or mayhave a multi-layered structure including a plurality of ferromagneticlayers. For example, the soft magnetic layer may have a dual filmstructure including CoFe layer and permalloy layer. As such, anappropriate combination of various films may be selected with regard tothe each application.

The ferromagnetic layer 1 and 2 may be made of the same material ordifferent materials.

An anti-ferromagnetic layer or a multi-layered film of nonmagneticlayer/ferromagnetic layer/anti-ferromagnetic layer may be additionallyprovided adjacent to the ferromagnetic layer 1 or 2 to fix the directionof magnetization of the ferromagnetic layer 1 or 2 and to control theresponse of the magnetoresistance effect element relative to themagnetic field. As the anti-ferromagnetic material for this purpose,FeMn, PtMn, PdMn, PdPtMn, or the like, are useful.

To obtain a desired value by controlling the element resistance, it isuseful to place a slight amount of conductor or semiconductor, or adifferent kind of element having the nature of an insulator, near theopening portion of the nanocontact.

FIGS. 7A and 7B are schematic diagrams that illustrate suchmagnetoresistance effect elements. In these specific examples, a regionD containing an additive element of a different kind is provided nearthe opening end of the micro through hole A. In this case, themagnetoresistance ratio may be sacrificed more or less; however, theresistance can be adjusted to a value the system using themagnetoresistance effect element requires. The region D including theadditive element may be formed in a layer. In this case, the thicknessof the layer D at the through hole A may preferably be in a range largerthan zero atomic layer and not larger than ten atomic layers.

By incorporating such an additive element, the exchange coupling betweenthe ferromagnetic layers 1 and 2 can be cut off, and it becomes easy tocontrol the magnetic domain structure. Further, by adding such anadditive element, the substantial size of the through hole A may bereduced and the magnetoresistance effect obtained with the nanocontactmay become more efficient.

As the additive element, noble metals, oxides, complex compoundsincluding oxide, or other elements which act as so-called “surfactant”for the growth of the magnetic layer can be used.

As the noble metal, metals such as copper (Cu), gold (Au) or silver (Ag)may be used. As the oxide, oxides such as Ni—O, Fe—O, Co—O, Co—Fe—O,Ni—Fe—O, Ni—Fe—Co—O, Al—O or Cu—O may be used. As the complex compound,compounds such as Al—Cu—O may be used. As the surfactant, surfactantssuch as antimony (Sb) or tin (Sn) may be used.

The magnetoresistance effect element according to the embodiment of theinvention can be easily manufactured and reliably formed into a deviceas compared with conventional magnetoresistance effect elements usingnanocontacts. A method of producing the magnetoresistance effect elementaccording to the embodiment of the invention will be explained below.

FIGS. 8A through D8 are cross-sectional views of stages of manufacturingthe substantial part of a magnetoresistance effect element.

Firsts referring to FIG. 8A, the ferromagnetic layer 1 is formed on asubstrate (not shown) directly or indirectly via a single layer, such asa buffer layer or a plurality of such layers, not shown, and theinsulating layer 3 is formed thereon. The insulating layer 3 may beformed by deposition or precipitation of a different kind of material onthe ferromagnetic layer 1, or by changing the nature of the surfacelayer of the ferromagnetic layer 1 by oxidation, nitrification orfluoridation, for example.

Next, as shown in FIGS. 8B and 8C, an electrically conductive needle 110having a tip in the form of a ball with a curvature radius in the rangefrom 5 to 1000 nm, cone or pyramid is brought into contact, and apressure is applied to form the micro through hole A in the insulatinglayer 3. In this process, a predetermined voltage is applied to aconductive wire 120 formed between the needle 110 and the magneticlayer, and the needle 110 is thrust until the current flowing in theconductive wire 120 reaches a predetermined value. That is, bymonitoring the current flowing between the needle 110 and theferromagnetic layer 1 upon thrusting the needle 110 into the insulatinglayer 3, the opening width of the micro through hole A is controlled.When the current reaches the predetermined value, the needle 110 ismoved back in the opposite direction and removed out of the surface ofthe insulating layer 3.

The needle 110 is driven by a distance-changing functional portion 130A(130B) as shown in FIGS. 8B and 8C. The distance-changing functionalportion 130 functions to move the needle 110 vertically of the samplesurface. For this purpose, there is the method of curving an arm asshown in FIG. 8B, or the method of moving it vertically as shown in FIG.8C, for example.

In the case of the curving method shown in FIG. 8B, the needle 110 isattached to an arm 140 extending in parallel to the sample surface, andthe distance-changing functional portion 130A located on and under thearm 140 is expanded or contracted to curve the arm 140, thus the heightof the needle 110 can be changed. The distance-changing functionalportion 130A may be a film that thermally expands upon a temperaturechange caused by heating with electricity. When such heating withelectricity is employed, an appropriate insulator is required betweenthe distance-changing functional portion 130 and the arm 140.

In the case of the vertical movement method shown in FIG. 8C, adistance-changing functional portion 130B such as a piezo element may beformed above the needle 110 such that the position of the needle 110 canbe controlled by the voltage applied to the piezo element.

Alternatively, a piezo element can be used as the distance-changingfunctional portion 130A shown in FIG. 8B. In this case, the curving ofthe arm 140 is controlled by applying a voltage to the piezo element.

The through hole formed by using such a mechanism capable of controllingthe minute distance basically has a predetermined diameter at thenarrowest portion, and defines spherical, conical, pyramidal, or otherconfiguration copying the needle 110.

In this manner, the micro through hole for obtaining desired conductanceis formed and is shaped conical, circular or pyramidal in accordancewith the tip configuration of the needle 110.

In the next step, as shown in FIG. 8D, the ferromagnetic layer 2 isdeposited toward the through hole. As a result, the ferromagnetic layers1 and 2 connect to each other with small conductance at the desiredmicro through hole A. Thereafter, annealing may be carried out ifnecessary. When the magnetoresistance effect element thus formed isused, electrodes are provided for respective ferromagnetic layers toenable their powering.

Through the method explained above, the magnetic nanocontact excellentin reproducibility and controllability is formed between theferromagnetic layers 1, 2. Typical values of the voltage applied uponthrusting the needle 110 are in the range of 0.01 through 10 V, thepredetermined current range is from 0.05 .mu.A to 100 mA, and theminimum opening width of the conical, circular or pyramidal through holeof the insulator is in the range from, 0.1 to 50 nm. The opening widthof the micro through hole is preferably limited within 0.1 to 20 nm.

The material used for the needle 110 is preferably harder than theinsulating layer 3 and electrically conductive. For example, conductivediamond, hard metal or silicon (Si) with or without a coating ofconductive diamond may be used.

The insulating layer 3 prior to formation of the magnetic nanocontact ispreferably as thin as possible within the range ensuring the function asthe insulating layer 3. More specifically, the range from 0.5 to 50 nmis preferable. The thickness of the ferromagnetic layer 1 and 2 may bedetermined appropriately depending upon the intended use. Theferromagnetic layer 1 may be a sufficiently thick bulk-shaped layer.

According to the embodiment of the invention, as shown in FIG. 9, thestructure having an array of a plurality of magnetoresistance effectelements on a common substrate (not shown) can be easily formed. Thiskind of structure is applicable to, for example, a patterned medium thatwill be explained later in greater detail.

The magnetoresistance effect element according to the embodiment of theinvention has the structure ready for making a device, and it istherefore employable for various purposes of use.

First, the magnetoresistance effect element can be used as a reproducingelement in a magnetic recording system. Since the use of themagnetoresistance effect element according to the embodiment ensures amagnetoresistance ratio as large as 20% or more, high reproductionsensitivity can be obtained.

FIGS. 10A through 10C are schematic diagrams that show specific examplesusing magnetoresistance effect elements according to the embodiment ofthe invention as magnetic reproducing elements.

In the case of the specific example shown in FIG. 10A, the ferromagneticlayer 2, insulating layer 3 and ferromagnetic layer 1 of themagnetoresistance effect element serially appear on the path of themagnetic flux released from the surface of the magnetic recording medium200 such that difference between directions of magnetization of theferromagnetic layers 1, 2 opposed to each other via the magneticnanocontact formed at the micro through hole A can be detected as achange of magnetoresistance. In this case, as illustrated here,directions of magnetization of these two ferromagnetic layers 1, 2 arepreferably put under domain control, if necessary.

In the case of the specific example shown in FIG. 10B, the ferromagneticlayer 2, insulating layer 3 and ferromagnetic layer 1 of themagnetoresistance effect element serially appear in the perpendiculardirection relative to the top surface of the magnetic recording mediumwithin the range of error angle about plus and minus 20 degrees. Hereagain, difference between directions of magnetization of theferromagnetic layers 1, 2 opposed to each other via the magneticnanocontact formed at the micro through hole A can be detected as achange of magnetoresistance.

In this case, magnetization M of the ferromagnetic layer 1 remoter fromthe recording medium 200 is preferably pinned in a direction within plusand minus 20 degrees from the perpendicular direction relative to thetop surface of the recording medium 200. For pinning the magnetization,a method of introducing a strong shape magnetic anisotropy, a method ofproviding an anti-ferromagnetic layer next to it and introducingunidirectional anisotropy, or the like, may be employed.

Direction of magnetization M of the ferromagnetic layer 2 nearer to therecording medium 200 is designed to be switchable by the magnetic fluxfrom the medium 200. In this manner, a signal from the recording medium200 can be detected from the angle made by the ferromagnetic layers 1, 2and magnetization M.

When the magnetoresistance effect element according to the embodiment isused, high sensitivity is obtained, and the surface opposed to therecording medium 200 can be readily formed and processed becausedistance from the medium 200 to the magnetic nanocontact A can bedetermined basically by adjusting the thickness of the ferromagneticlayer 2. When the medium-opposed surface opposed to the recording medium200 is easy to process, it is also possible to locate the ferromagneticlayer 1 nearer to the recording medium 200 as shown in FIG. 10C.

FIGS. 11A and 11B are schematic diagrams that show other specificexamples using magnetoresistance effect elements according to anembodiment of the invention as magnetic reproducing elements. In thesespecific examples shown here, the film surface of the magnetoresistanceeffect element is oriented perpendicularly to the medium 200. The microthrough hole A is out of a center of symmetry in a major plane of theinsulating layer 3 toward the medium 200. Since the signal magneticfield becomes larger as the distance from the medium decreases, thisstructure is advantageous for increasing the detection efficiency of themagnetic field of the free layer 2.

The ferromagnetic layer 2 serving as a magnetization sensitive layer(free layer) may be a single layer as shown in FIG. 11A, or atwo-layered film as shown in FIG. 11B. In case of the specific exampleshown in FIGS. 11A, the ferromagnetic layer 1 forms a “pinned layer”pinned in the direction of magnetization. The ferromagnetic layer(pinned layer) 1 may be a multi-layered structure stacked, sequentiallyfrom the nearest to the micro through hole A, a magnetic layer and ananti-ferromagnetic layer, or a magnetic layer, nonmagnetic layer,magnetic layer and anti-ferromagnetic layer. In FIG. 11A, the stackedstructure is sandwiched by a pair of magnetic shields SH.

In case of the specific example of FIG. 11B, the ferromagnetic layer(pinned layer) 1 may be a multi-layered structure of ferromagneticlayer/anti-ferromagnetic layer/ferromagnetic layer. The ferromagneticlayer 1 may also be a multi-layered structure of ferromagneticlayer/nonmagnetic layer/ferromagnetic layer/anti-ferromagneticlayer/ferromagnetic layer/nonmagnetic layer/ferromagnetic layer.

As shown in FIG. 11B, free layers 2A and 2B are provided through thethrough hole A at opposite sides of pinned layer 1. These free layers 2Aand 2B sense the magnetic signals respectively from the recording medium200. As shown in FIG. 11C, when the magnetic signals for the free layers2A and 2B are both upward, the resistance change ΔR becomes zero sincethe magnetization direction of the free layers 2A and 2B are the same asthe magnetization direction of the pinned layer 1. In contrast, when themagnetic signals for the free layers 2A and 2B are both downward, theresistance change ΔR becomes 2 (in arbitrary units) since spinscattering occurs between pinned layer 1 and free layer 2A and betweenpinned layer 1 and free layer 2B, respectively.

When one of the magnetic signals for the free layers 2A and 2B isdownward and another is upward, the resistance change ΔR becomes 1 (inarbitrary unit) since spin scattering occurs only between pinned layer 1and free layer 2A or between pinned layer 1 and free layer 2B.

Thus, as shown in FIG. 11C, the each case can be distinguished bymonitoring the resistance change ΔR.

Therefore, by providing a plurality of free layers, a multi-valued (morethan two) resistance change can be realized. In the case of nanocontactMR element according to the embodiment, it becomes easy to realize sucha multi-valued recording/reproducing since a resistance change more than100% can be possible.

The magnetoresistance effect element according to the embodiment isapplicable to a so-called “patterned medium”. That is, the structurehaving an array of a plurality of magnetoresistance effect elements asshown in FIG. 9 can be made easily. One of such applications is amagnetic memory device. Another of such applications is a recordingmedium for a probe-storage system.

FIG. 12 is a schematic diagram illustrating a cross-sectional structureof the substantial part of a magnetic memory device usingmagnetoresistance effect elements according to an embodiment of theinvention.

As illustrated, the magnetic memory device according to the embodimentof the invention has the structure including a parallel alignment of aplurality of magnetoresistance effect elements 10 on an electrode layer20. The magnetoresistance effect elements are electrically isolated fromeach other by an insulating layer 30, and each has the role of arecording/reproducing cell.

To access to each recording/reproducing cell 10, a conductive probe PRas an upper electrode may be used as shown in FIG. 13A, or a fixedwiring WR may be used as shown in FIG. 13B. In the model using the fixedwiring WR, it contacts the cell 10. However, in the model using theconductive probe PR, it may be either contacted or uncontacted with thecell 10. In case the probe PR does not contact the cell, a tunnelingcurrent flowing between it and the cell 10 enables probing.

FIGS. 14A through 15H are schematic diagrams that show cross-sectionalstructures of magnetoresistance effect elements 10 that can be used inthe magnetic memory device of FIG. 12. Any of the magnetoresistanceeffect element of FIGS. 14A through 14D and those of FIGS. 15A through15H has a structure forming a magnetic layer on the second ferromagneticlayer 2 via a nonmagnetic layer 4. Further, a pair of electrodes areconnected to both sides of the stacked structure. Each magnetoresistanceeffect element functions for both recording and reproduction. That is,recording is enabled by supplying a current of a predetermined magnitudeto the magnetoresistance effect element in a predetermined direction,and a signal of the cell can be read from a resistance value measured bysupplying a weaker current.

The cell shown in FIG. 14A has a structure in which a nonmagneticintermediate layer 4 and a ferromagnetic layer 5 are stacked on thesecond ferromagnetic layer 2. The first ferromagnetic layer 1 and theferromagnetic layer 5 are fixed in magnetization M (shown by the arrow)beforehand such that directions of magnetization are anti-parallel.Magnetization in anti-parallel directions enables writing with a smallercurrent as explained later.

When a current is supplied to this kind of multi-layered structure toflow vertically to the film plane, recording and reproduction areenabled using the second ferromagnetic layer as the recording portion.That is, when the current flows through the first ferromagnetic layer 1or the ferromagnetic layer 5, conduction electrons receive spininformation corresponding to the magnetization direction of the magneticlayer. When the electrons enter into the second ferromagnetic layer 2,if the spin direction those electrons have coincides with the spindirection corresponding to the magnetization direction (shown by thearrow) of the second ferromagnetic layer 2, the electrons can easilypass the second ferromagnetic layer 2. However, if they areanti-parallel, the electrons are reflected and cannot easily pass thesecond ferromagnetic layer 2.

At that time, conductance between the ferromagnetic layer 1, 2 is small,and the change of the magnetoresistance between them is large. On theother hand, conductance between the ferromagnetic layers 2, 5 is large,and the change of magnetoresistance between them is small. Therefore, inthe model of FIG. 14A in which they are serially aligned, the formerconductance between the ferromagnetic layer 1, 2 is dominant, and thedevice results in detecting the difference between magnetizationdirections of the ferromagnetic layers 1, 2. That is, an increase ordecrease of the electric resistance is observed in accordance with themagnetization direction of the second ferromagnetic layer 2, andinformation corresponding to the magnetization direction can be readout.

On the other hand, in case a predetermined amount of current is suppliedto flow vertically to the film plane for recording, conduction electronsfirst receive spin information of magnetization M held by one of thefirst ferromagnetic layer 1 and the ferromagnetic layer 5 where theelectrons first enter. Thereafter, the electrons enter into the secondferromagnetic layer 2. In this case, if a large quantity of electronsenters into the ferromagnetic layer 2, magnetization direction of thesecond ferromagnetic layer 2 changes in accordance with the spininformation those electrons have. That is, direction of magnetization Mheld by one of the first ferromagnetic layer 1 and the ferromagneticlayer 5 where the electrons first enter tends to be copied to the secondferromagnetic layer (recording layer) 2.

Electrons passing through the ferromagnetic layer 2 receive spininformation of the first-passing layer of 1 and 5 in the form ofreaction and tend to orient in the opposite direction. Because of thesetendencies, magnetization direction can be controlled by adjusting thedirection of the current.

Although FIGS. 14A through 14D show models of parallel-to-planemagnetization, i.e., magnetization directions parallel to the filmplane, models of perpendicular magnetization as shown in FIGS. 15A, 15Cand 15J ensure the same effects. Also regarding the cross-sectionalgeometry of the nanocontact, it may be narrowed downward as shown inFIGS. 14 through 14D, upward as shown in FIGS. 15B through 15H, or mayhave any of other various configurations as shown in FIGS. 6A through6C.

In the magnetoresistance effect elements shown in FIGS. 14A through 15H,direction of magnetization M (shown by the arrow) of the secondferromagnetic layer (recording layer) 2 changes with the flowingdirection of a current above a critical value. This direction ofmagnetization of the ferromagnetic layer (recording layer) 2 is used torecord a signal. The signal can be read from the resistance valueappearing when a current lower than the critical current value forwriting is supplied.

For this purpose, it is necessary to place the ferromagnetic layers 1and 5 above and below the second ferromagnetic layer 2 serving as therecording layer and to pin their magnetization M in anti-paralleldirections.

FIGS. 14B through 14D and FIGS. 15D through 15H show structuresconfigured to pin their magnetization.

In FIG. 14C, the cell has the structure including a nonmagneticintermediate layer 4A, ferromagnetic layer 5A, nonmagnetic intermediatelayer 4B, ferromagnetic layer 5B, and anti-ferromagnetic layer 6A thatare sequentially stacked in the described order on the secondferromagnetic layer 2. The cell further includes an anti-ferromagneticlayer 6B below the first ferromagnetic layer 1. In this manner, thefirst ferromagnetic layer 1 and the ferromagnetic layer 5 can be pinnedin magnetization M. The micro through hole may have its wider openingoppositely arranged as shown in FIG. 15D. In all the cells shown inFIGS. 14A through 15H, there is no up-and-down limitation. Further,direction of magnetization is not limited to parallel-to-planemagnetization, but may be perpendicular-to-plane (perpendicularmagnetization) as shown in FIG. 15F.

In the cell of FIG. 14C, the nonmagnetic intermediate layer 4A,ferromagnetic layer 5A and anti-ferromagnetic layer 6A are stacked inthe described order on the second ferromagnetic layer 2. The cellfurther includes the nonmagnetic intermediate layer 4B, ferromagneticlayer 5B and anti-ferromagnetic layer 6B located under the firstferromagnetic layer 1 sequentially from the nearest thereto. Here again,the first ferromagnetic layer 1 and the ferromagnetic layer 5 can bepinned in magnetization, respectively.

In the cell of FIG. 14D, the nonmagnetic intermediate layer 4A,ferromagnetic layer 5A, nonmagnetic intermediate layer 4B, ferromagneticlayer 5B and anti-ferromagnetic layer 6A are stacked in the describedorder on the second ferromagnetic layer 2. The cell further includes anonmagnetic intermediate layer 4C, ferromagnetic layer 5C andanti-ferromagnetic layer 6B located under the first ferromagnetic layer1 sequentially from the nearest thereto. Here again, the firstferromagnetic layer 1 and the ferromagnetic layer 5 can be pinned inmagnetization, respectively.

In magnetoresistance effect elements shown in FIGS. 14A through 14D andFIGS. 15A through 15D, magnetization directions of the ferromagneticlayers 1 and 5 are anti-parallel. Due to anti-parallel magnetizationdirections, spin transmission and an effect of reaction are added, andwriting to the recording layer 2 is accomplished efficiently.

From the viewpoint of easier fabrication, models using parallelmagnetization directions of the ferromagnetic layers 1 and 5 as shown inFIGS. 15F through 15H are preferable. Effectiveness of spin transmissionoperation and reaction vary with the area in contact with the recordinglayer 2. Therefore, at the cost of slight increase of the reversingcurrent, directions of magnetization of the ferromagnetic layers 1 and 5can be aligned in parallel. Thus, the number of layers stacked forpinning can be decreased, or the number of steps in the manufacturingprocess can be reduced.

FIGS. 16A through 16E are schematic cross-sectional views that showother specific examples of magnetoresistance effect elements usable inthe magnetic memory device of FIG. 12. In all these specific examplesshown here, one of the first and second ferromagnetic layers 1, 2 ismagnetically pinned in a predetermined direction, and the other isvariable in magnetization direction (shown by the arrow). Additionally,a pair of electrodes 7 are provided outside the first and secondferromagnetic layers (opposite sides remoter from the intermediate layer3) so as to carry out recording or reproduction by supplying a currentfrom a current supply means to these electrodes 7 by direct or indirectcontact such that the current flows through interfaces between everyadjacent stacked film.

For pinning the magnetization of the ferromagnetic layer, ananti-ferromagnetic layer may be formed on the outer surface of themagnetic layer, or nonmagnetic/ferromagnetic/anti-ferromagnetic layersmay be stacked.

Reproduction and recording can be executed by bringing about spintransmission and reaction effect between the ferromagnetic layers 1 and2 as explained above by detecting the magnetoresistive effect of theelement itself for reproduction and supplying a current larger than thereproducing current for recording. The structures shown in FIGS. 16Athrough 16E are advantageous in that the structures are very simple,although the device property is somewhat difficult to adjust.

Also in the magnetoresistance effect elements shown in FIGS. 16A through16E, cross-sectional geometry of the micro through hole is not limitedto the illustrated conical shape, but may be modified to a circular,pyramidal, prismatic, spherical or other geometrical shape.

The micro through hole in the insulating layer 3 is preferred to belocated between the electrodes 7, 7 which cover the ferromagnetic layers1 and 2 partly or completely in order to supply the current. Therefore,in the case in which the electrodes 7, 7 cover these layers 1 and 2partly as shown in FIG. 16E, the micro through hole is set up at anoff-center position relative to a center of the element.

EXAMPLES

Herein below, embodiments of the invention will be explained in greaterdetail in conjunction with examples.

First Example

As the first example of the invention, there is a model ofmagnetoresistance effect element a magnetic nanocontact on nickel (Ni)covered by alumina.

First of all, for obtaining the multi-layered structure shown in FIG.8A, aluminum (Al) was deposited by vapor deposition on a ferromagneticlayer 1 made of nickel, and its top surface was oxidized to form aluminaas an insulating layer.

After that, a needle 110 coated with conductive diamond and used to forma micro through hole was driven close to the top surface of alumina asshown in FIG. 8B. Then, the voltage of 0.01 V was applied across thenickel layer 1 and the needle 110, and while monitoring the flowingcurrent, the needle 110 was driven into the alumina insulating layer 3.Movement of the needle 110 was controlled by making use of thermalexpansion caused by electric heating of a distance-changing functionalportion 130A attached to an upper portion of the arm 140.

FIGS. 17A and 17B are graph diagrams that show changes in distancebetween the top surface of the ferromagnetic layer 1 and the tip portionof the needle 110 and changes in current flowing between them with time,when the needle 110 is driven at a constant speed.

In the example shown here, distance was linearly changed with time, butthe flowing current increase exponentially. The set current was adjustedto 10A, and when the actual current reached the set current, the curveof the arm 140 supporting the needle 110 was released. Additionally,nickel was deposited by vapor deposition as the ferromagnetic layer 2 tobury the through hole made by the needle 110.

Electrodes were provided in association with the ferromagnetic layers 1,2 of the magnetoresistance effect element obtained, and itsmagnetoresistive effect was measured.

FIG. 18 is a graph diagram showing a relation between applied magneticfield and electrical resistance in the magnetoresistance effect elementaccording to the embodiment of the invention. Although more or lesshysteresis was observed, resistance substantially decreased when amagnetic field was applied. Resistance at the contact portion of themicro through hole A was approximately 3 kΩ when the magnetic field waszero, and MR ratio as large as 120% was obtained.

Second Example

As the second example of the invention, a reproducing element formagnetic recording was prepared by using the manufacturing method usedin the first embodiment explained above.

That is, a thick cobalt (Co) film was formed on the substrate, andalumina was formed thereon. Then, after making the micro through hole A,20 nm thick Permalloy was deposited by vapor deposition. Part of thePermalloy above the micro through hole A was patterned into anapproximately 20×20 nm square, and part of the underlying cobalt layeras large as 100 mn was cut out. A conductive wire was provided thereto,and the magnetoresistance effect element was moved on the surface of thevertically magnetized medium. As a result, a change of resistancecorresponding to the change of the medium signal was observed.

Third Example

As the third example of the invention, the magnetic memory device shownin FIG. 12 was prepared.

More specifically, the multi-layered film shown in FIG. 14D was formedon a conductive substrate by using a sputtering apparatus. In the sameprocess, the micro through hole A was also formed.

That is, layers from the anti-ferromagnetic layer 6B to the firstferromagnetic layer 1 were deposited on the electrode layer 20, and apolymer was coated thereon as the insulating layer. Then the microthrough hole A was formed, and the second ferromagnetic layer wasdeposited thereon.

Additionally, layers from the nonmagnetic intermediate layer to theanti-ferromagnetic layer 6A were formed as shown in FIG. 14D. Then apolymer having a phase separation structure was coated thereon, therebyto form a mask for micro fabrication. Its surface is next selectivelyetched by ion milling to form a patterned medium. Spaced cell patternswere buried with a polymer to smooth the surface.

By supplying a current to one of cells of the patterned medium thusobtained by using a probe as an electrode, a recording and reproducingtest was carried out. In this case, the plus direction corresponds tothe flowing direction of the current from the top to the bottom in FIG.14D. Thus the resistance of the cell was measured with the current of 10μa. At that time, resistance value was 3 kΩ. Additionally, writing wascarried out by supplying the recording current of minus 500 μa, and as aresult of measurement of the cell resistance here again with the currentof 10 μm, resistance value was 7 kΩ.

Although a certain degree of hysteresis was observed, the resultdemonstrated that current-driven writing and current-driven reading werepossible.

Fourth Example

As the fourth example of the invention, magnetoresistance effectelements including an additive element introduced at the through holewere prepared.

FIGS. 19A and 19B are schematic diagrams showing a cross-sectionalstructures of the substantial part of a magnetoresistance effectelements experimentally prepared in an embodiment of the invention. Asshown in these figures, the layered region D including the additiveelement was formed on or below the insulating layer 3 in these MRelements.

The inventors have also formed MR elements where an additive element wasintroduced only at the through hole A as shown in FIG. 7A. The inventorshave also formed MR elements where as additive element was notintroduced.

In all the MR elements, the deposition process was performed by using anion beam sputtering system and the etching process was performed byemploying an electron beam (EB) reactive etching. The details of the EBreactive etching will be explained with reference to the eleventhexample of the present invention.

The intended diameter of the through hole was set to be 10 nm for allsamples. The structures of the samples I through V will be explainedherebelow.

A sample I has a structure shown in FIG. 19A where three atomic layersof copper (Cu) were inserted as the layered region D. The ferromagneticlayer 1 has a multi-layered structure of PtMn 15 nm/CoFe 4 nm/Ru 1nm/CoFe 4 nm. This ferromagnetic layer 1 was made to be the pinnedlayer. As the material of the insulating layer 3, SiO₂ was employed.After growing the SiO₂ layer having a thickness of 3 nm, the throughhole A was formed.

By incorporating the copper layer as the additive element, the magneticcoupling between the ferromagnetic layers 1 and 2 can be effectively cutoff while maintaining the crystallinity at the nanocontact portion. Bycutting the magnetic coupling between the ferromagnetic layers 1 and 2,the magnetization of the free layer 2 can shift more freely.

In the conventional MR element, even in the case where an intermediate(spacer) layer of copper is provided, a magnetic coupling between theferromagnetic layers provided at opposite sides thereof may beinevitable since an exchange interaction can occur therebetween at thethin portion of the copper intermediate layer.

In contrast to this, by employing the magnetic nanocontact according tothe embodiment of the invention, the magnetic coupling between theferromagnetic layers 1 and 2 is effectively cut off since theinter-layer exchange interaction therebetween becomes negligible.

In sample I, the ferromagnetic layer 2 was made of CoFe of 4 nm inthickness. A copper layer (not shown) was deposited on the ferromagneticlayer 2 as a protective film.

Next, a sample II has a structure shown in FIG. 19B, where an alloylayer of copper (Cu) and aluminum (Al) was deposited and oxidized in anoxygen atmosphere to form a Cu—Al—O layer as the layered region D. Theferromagnetic layers 1 and 2 were same as the sample I. The insulatinglayer 3 was made of Al₂O₃.

The Cu—Al—O layer is apt to include high resistive particles which havean aluminum-rich composition and conductive regions which have acopper-rich composition. Therefore, the effective through hole size canbe reduced and the resultant magnetoresistance effect becomes evenlarger.

A sample III has a structure shown in FIG. 7A, where oxygen (O) wasintroduced by a natural oxidation as the additive element. The basicstructure of the sample is same as the sample I except for the additiveelement and its introduction process. In the case of sample III, theeffective through hole size can be reduced by introducing oxygen as theadditive element in analogy with the aforementioned sample II.

A sample IV has a magnetic nanocontact made of permalloy only, where noadditive element was introduced.

A sample V has a conventional CCP-MR structure including a multi-layeredstructure of PtMn 15 nm/CoFe 4 nm/Ru 1 nm/CoFe 4 nm/Cu 2 nm/CoFe 4nm/Cu.

A magnetoresistance ratio of each sample was measured and listed inTable 1 shown below. The samples I through IV have magnetoresistanceratios much larger than the sample V having a conventional CCP-MRstructure. The samples I and II have the largest magnetoresistanceratio.

TABLE 1 Sample Sample Sample Sample Sample I II III IV Vmagnetoresistance ratio 147% 112% 43% 76% 4%

Fifth Example

As the fifth example of the invention, a so-called “tandem type” elementwith a serially stacked a plurality of magnetoresistance effect elementswas prepared.

FIG. 20 is a schematic diagram showing a cross-sectional structure ofthe substantial part of a magnetoresistance effect elementexperimentally prepared in an embodiment of the invention.

As illustrated, ferromagnetic layers 1 and insulting layers 3 werealternately accumulated, and a micro through hole A was formed in eachinsulating layer 3 so as to connect upper and lower ferromagnetic layers1 via a magnetic nanocontact of each insulating layer 3. That is,ferromagnetic layers 1 and 2 in the magnetoresistance effect elementshown in FIG. 1A or 1B were commonly used by adjacent magnetoresistanceeffect elements.

Positions of the micro through holes A formed in individual insulatinglayers 3 need not be aligned linearly as shown in FIG. 20.

The serial structure according to this example is advantageous in that alarger change of magnetoresistance can be obtained.

In this kind of multi-layered serial structure, if the micro throughholes A are not equal in opening width, the entire property is regulatedby one of micro through holes A having the largest resistance.Therefore, this structure can compensate the possible defect that themicro through holes A tend to become too large.

Sixth Example

As the sixth example, a magnetoresistance effect element having acolumnar micro through hole is explained.

FIG. 21 is a schematic diagram showing a cross-sectional structure ofthe substantial part of a magnetoresistance effect element prepared asthis example.

First, an anti-ferromagnetic layer 6 and a magnetic layer 1 weresequentially formed on a conductive substrate S, and an alumina layer 3having a columnar micro through hole A having the diameter of 5 nm wasformed thereon. The micro through hole A was buried with nickel (Ni)using an electrochemical deposition method. Then, by forming themagnetic layer 2 thereon, a magnetoresistance effect element having thestructure shown in FIG. 21 was obtained.

FIG. 22 is a graph diagram showing changes of magnetoresistance of amagnetoresistance effect element according to the instant example of theinvention. Electric resistance under zero magnetic field was relativelysmall, namely not larger than 100Ω, and a large decrease of resistancecould be obtained under a magnetic field of 20 G or more.

Seventh Example

As the seventh example of the invention, a reproducing element formagnetic recording having the structure shown in FIG. 11A was prepared.A cross-sectional structure (on the opening surface) of the elementviewed from the medium 200 appears as shown in FIGS. 23. Materials andthicknesses of respective layers of the magnetoresistance effect elementexcept for a part of electrode layers EL and magnetic shield layers SH,are as follows.

Ta 5 nm/CoFe 1 nm/opening in the SiO₂ layer/CoFe 1 nm/Ru 1 nm/CoFe 1nm/PtMn 30 nm/Ta 5 nm

The opening was made by using FIB (focused ion beam) processing. On sidesurfaces of the magnetoresistance effect element, hard magnet layers HMwere formed to control magnetization of the free layer 2. Part of thefree layer 2 nearest to the hard magnet layers HM function as aninsensitive region 2A for control of magnetization. Therefore, since themagnetoresistive effect of the insensitive region 2A is also included,the detection efficiency degrades. Additionally, since the signalmagnetic field from the medium 200 becomes weaker with an increase ofdistance from the medium 200, response of the free layer 2 degrades, andthe detection efficiency degrades again.

In contrast, in the structure employed as the instant example, it ispossible to exclude the insensitive region 2A and detect the statesensed exclusively in the only portion near the medium 200. That is,this example minimizes the sensitivity loss, and can enhance thedetection efficiency to 1.5 time or more of the detection efficiency ofa simple structure of free layer/intermediate layer/pinned layer.

Eighth Example

As the eighth example, a 32×32 matrix was formed by arrangingmagnetoresistive cells having the structure shown in FIG. 15G on asubstrate as shown in FIG. 12. Then, 32×32 such matrices were arrangedto form a recording/reproducing medium of 1 Mbit (megabit) in total.

Using 32×32 probes, recording and reproduction were carried out with therecording/reproducing medium. That is, one probe was associated witheach matrix. An aspect of the probing is shown in FIG. 13A. A cell foreach probe PR was selected by means of an XY drive mechanism associatedwith the medium.

These probes PR were connected in an array via transistors TR as shownin FIG. 24. Then by selecting a bit line BL and a word line WL andthereby turning ON a transistor TR associated with a particular probePR, the probe was selected. This structure was confirmed to enableselection of a number of bits.

Ninth Example

As the ninth example, a magnetoresistance effect element having thecross-sectional structure shown in FIG. 5D was prepared by using a“self-organizing process”.

First, using an ultrahigh vacuum ion beam sputtering apparatus, a flatferromagnetic layer 1 of CoFe was formed on a substrate. Thereafter, thesubstrate temperature was raised to 200° C., and a SiO₂ layer 3 wasgrown thereon. Depending on the condition, the SiO₂ layer grows in theform of islands.

FIGS. 25A through 25C are schematic diagrams showing plan-viewedconfigurations of a SiO₂ layer 3 (on the ferromagnetic layer 1) thatchanges with growth time.

The SiO₂ layer 3 appears as minute islands as shown in FIG. 25A in itsinitial growth period and larger islands in the middle growth period,then grows to connect the islands and finally becomes a continuous film.

On each of these different aspects of the SiO₂ layer 3 during itsgrowth, a CoFe ferromagnetic layer 2 was deposited, and themagnetoresistive effect was examined.

FIG. 26 is a graph diagram showing growth time of the SiO₂ layer on theabscissa and MR ratio on the ordinate. In the initial period of thegrowth, since the ferromagnetic layers 1 and 2 contact over a wide area,the MR effect is very small. However, as the growth of the SiO₂ layer 3progresses to diminish the contact area between the ferromagnetic layer1 and 2 to an appropriate degree, the MR ratio rapidly increases. Whenthe growth of the SiO₂ layer 3 further progresses, since it covers thesurface of the ferromagnetic layer 1, the MR ratio passes the peak andrapidly decreases. It is presumed that the TMR effect appears under thecondition immediately after the SiO₂ layer 3 covers the surface of theferromagnetic layer 1. However, since the insulating layer 3 becomesthicker with progress of the growth, the MR ratio rapidly decreases.

As explained above, according to the method of this example, a large MRvalue can be obtained by forming the micro through hole without makingfree use of micro-fabrication technologies.

Tenth Example

As the tenth example of the invention, cells having magnetizationdirections related as shown in FIG. 16A were fabricated by the samemethod as the eighth example, and the magnetic recording medium of FIG.12 was formed.

After a PtMn layer (10 nm thick) was formed on a base layer 20 by usingan ultrahigh vacuum sputtering apparatus, a Co layer (5 nm thick) 1 wasgrown. Islands of an alumina layer 3 were further formed, and a Co layer(2.5 nm) 2 was formed thereon. Additionally, a Ta layer (3 nm) wasformed thereon. After this multi-layered film was annealed in a vacuummagnetic field, a cell array of regular alignment of cells each sized 70nm×120 nm was formed by using an EB (electron beam) exposure apparatus.

Using this array, a probe PR was brought into contact with one of thecells, and a resistance change of the element appearing upon sweepingthe current value was examined. As a result, resistance of the elementincreased under the flow of a current not smaller than plus 1.2 mA; whenthe current was supplied up to 2 mA and the direction of the current wasreversed thereafter, the resistance value remained large up to nearminus 1.4 mA; and when the current value was increased from that currentvalue as a border further to the minus direction, resistance decreased.This kind of response of resistance change was similarly reproduced insome repeated experiments. The changing ratio of resistance by currentsweep was 22% on average.

Heretofore, some models of magnetoresistance effect elements accordingto embodiments of the invention and some manufacturing methods thereofhave been explained with reference to FIGS. 1A through 26.

Herein below, the manufacturing methods of the micro through hole formedin magnetoresistance effect elements according to the embodiments of theinvention will be explained.

According to a first manufacturing embodiment of the invention, amanufacturing method of a magnetoresistance effect element comprises:forming an insulating layer on a first ferromagnetic layer; forming ahole reaching said first ferromagnetic layer by thrusting a needle fromthe top surface of said insulating layer; and depositing a ferromagneticmaterial to form a second ferromagnetic layer which buries said hole andoverlying said insulating layer.

In the method, a current flowing between said first ferromagnetic layerand said needle may be monitored, and thrusting of said needle may beinterrupted when said current reaches a predetermined value.

According to another manufacturing embodiment of the invention, amanufacturing method of a magnetoresistance effect element comprises:limiting electrical conduction between upper and lower magnetic layerssandwiching an insulating layer substantially to an irradiated region bya irradiation with a converged flux of charged particles.

According to yet another manufacturing embodiment of the invention, amethod of fabricating a magnetoresistance effect element comprises:etching an insulating layer by supplying a reaction gas onto a surfaceof said insulating layer and by irradiating said insulating layer with aconverged electron beam to compose a volatile gas; and burying theetched region with a magnetic layer which is one of components of saidmagnetoresistance effect element.

According to yet another manufacturing embodiment of the invention, amethod of fabricating a magnetoresistance effect element comprises:etching an insulating layer surface with a converged ion beam; andburying the etched region with a magnetic layer which is one ofcomponents of said magnetoresistance effect element.

According to yet another manufacturing embodiment of the invention, amethod of fabricating a magnetoresistance effect element includes: afirst ferromagnetic layer; an insulating layer overlying said firstferromagnetic layer; and a second ferromagnetic layer overlying saidinsulating layer, said insulating layer having a hole formed therein,said first ferromagnetic layer and said second ferromagnetic layer beingconnected to each other via said hole, said method comprises: changing acrystal arrangement of at least one of said first and secondferromagnetic layers by irradiating with a electron beam.

Herein below, other specific examples related to the manufacturingmethods according to the embodiments of the invention will be explainedwith reference to FIGS. 27 through 67.

Eleventh Example

As the eleventh example of the invention, a specific example of forminga micro through hole by etching using an electron beam will beexplained.

FIG. 27 is a schematic diagram for explaining the method used in thisexample. This apparatus includes an EB source 310 located in a vacuumchamber 300 to supply an electron beam, a sample stage 320, a nozzle 340for supplying a reaction gas to the sample, and a sample heater 330 forraising the temperature of the sample. The vacuum chamber 300 isevacuated through an exhaust port 350 to maintain a low-pressureatmosphere.

Boring of the micro through hole was carried out in the followingmanner.

A sample having the ferromagnetic layer and the insulating layer 3 isfirst fixed on the sample stage 320. By monitoring the scanned EB image,the boring position of the insulating layer 3 is determined. Theintended position is concentrically irradiated with an electron beam,and the reaction gas was blown around it through the nozzle 340.Additionally, for the purpose of promoting the reaction, the temperatureof the sample was adequately raised by using the sample heater 330. As aresult, the supplied gas and EB act on the surface of the insulatinglayer 3, and make it vaporize as a volatile substance. Thus, the etchingis promoted. Additionally, the rise of the sample temperature enhancesthe reaction speed and shortens the process time. Moreover, formation ofa carbon fluoride layer is prevented on the magnetic layer 1, which isthe end point reluctant in reaction, by EB irradiation.

FIG. 28 is a schematic diagram showing a process of fabricating amagnetoresistance effect element. That is, it shows the process offorming the micro through hole A in the SiO₂ layer 3 formed on the CoFemagnetic layer 1.

First, a PtMn anti-ferromagnetic layer (for example, 15 nm thick), notshown, is formed on a base film, not shown, (made of t nm thicktantalum, for example). After that, the CoFe layer 1 is formed thereonas the pinned layer of the MR element. Then a 3 nm thick SiO₂ layer 3 isformed thereon.

In the next step, an electron beam concentrated to a beam diameter notlarger than 10 nm is irradiated onto a spot on the surface of the SiO₂layer 3. For the purpose of preventing the insulator from charging up,the EB acceleration voltage was adjusted to 10 kV. Under this condition,XeF₂ is blown as the reaction gas. As a result, SiO₂ acts on the gas andvaporizes as a silicon fluoride. However, since the reaction gas makesno reaction product with the CoFe magnetic layer 1, reaction stops afteretching only the SiO₂ layer 3.

To prevent influences of charge-up, it is recommended to decline thesample by approximately 30 degrees or promote emission of secondaryelectrons. The reaction gas to be supplied from the nozzle 340 is notlimited to XeF₂, but CHF₃ or other Freon-family gases are alsoeffective. As an additional or alternative countermeasure againstcharge-up, a metal film such as Nb (niobium) film may be formed on theSiO₂ layer 3.

FIG. 29 shows an example having formed a Nb film 400. Thickness of theNb film 400 may be, for example, around 3 nm. In this case, an electronbeam is irradiated using CF₄ as the reaction gas to form spot throughholes 400A in the Nb film 400. Thereafter, the reaction gas is replacedby XeF₂, and the SiO₂ layer 3 is selectively etched by EB irradiation.

As such, the metal film 400 formed on the insulating layer 3 preventsthe diameter of EB irradiation from being enlarged by charge-up.Additionally, the metal film 400 overlying the insulating layer 3improves the crystallographic property of the magnetic film formedthereon, and thereby enhances the soft magnetism and the resistancechange. That is, it contributes to improvement of the magnetic fieldsensitivity of the magnetoresistance effect element.

FIGS. 30A through 30C are cross-sectional views showing another processof forming a nanocontact.

It takes much time to form the micro through hole A by EB in eachelement one by one. The process time for making the micro through holesA by EB can be shortened by forming the metal film 400 alone as shown inFIG. 30A, and thereafter carrying out RIE (reactive ion etching) by CFH₃gas over the entire wafer as shown in FIG. 30B, or selectively etchingthe SiO₂ layer 3 throughout the entire wafer by CDE (chemical dryetching) producing less physical damage.

It is also possible to copy the through hole 400A in the metal to theinsulating film as shown in FIG. 30C by carrying out sputtering etchingor ion milling over the entire wafer after making the through holes 400Ain the metal film 400 as shown in FIG. 30A. This method is alsoeffective to reduce the process time because the micro through holes Acan be formed simultaneously throughout the entire wafer.

After the micro through holes A are formed in the SiO₂ layer 3, themagnetic layer 2 (for example, approximately 5 nm thick CoFe) to be usedas the free layer is formed as shown in FIG. 31A, and an approximately 5nm thick Ta film 5 is formed as a protective layer. Through these steps,the MR multi-layered film having point contacts between the pinned layerand the free layer can be obtained.

As shown in FIG. 31B, an approximately 2 nm thick Cr film or Cu film tobe used as the nonmagnetic intermediate layer (spacer layer) in the MRelement may be formed before the CoFe magnetic film 2 as the free layeris formed. This is effective for facilitating magnetic reversal of thecontact portion of the free layer 2 under an external magnetic field andfor rendering it responsive to a lower level signal magnetic field.

The same effect will also be obtained when the nonmagnetic intermediatelayer 4 is formed on the pinned layer 1 as shown in FIG. 31C.

On the other hand, upper and lower magnetic layers may be reversed touse the lower as the free layer and the upper as the pinned layer.

FIG. 32A shows an example in which the upper and lower layers areinverted. In this example, after the micro through hole A is formed, theCoFe layer 1 as the pinned layer, anti-ferromagnetic layer 6 formagnetically pinning the CeFe film 1, and Ta protective film 9 areformed. Since the magnetic film 1 buried in the micro through hole A isinevitably liable to contain crystal defects, a model burying the holewith a pinned layer not required to have a soft-magnetic property ismore advantageous from the viewpoint of sensitivity to the signalmagnetic field. Even when the magnetic film 2 as the pinned layer isburied, the nonmagnetic intermediate layer may be first buried as shownin FIG. 32B. Here again, magnetic reversal of the free layer 1responsive to the signal magnetic field takes place smoothly, andsensitivity to a low level signal magnetic field can be enhanced.

Even when a spacer layer is formed on the free layer 2 as shown in FIG.32C, the same effect will be obtained.

To ensure good crystalline property of the buried magnetic layer 2 andthereby obtain a high MR, the micro through hole A preferably has amoderately tapered side surface and is preferably minimized in surfaceroughness. To make a moderate taper, it is recommended to process theinsulating film 3 by etching, such as ion milling with an oblique angleof incidence as shown in FIG. 33 or RIBE (reactive ion beam etching)with an oblique angle of incidence. To minimize the surface roughness ofthe tapered surface, SiO₂, alumina or an amorphous oxide is preferablyused as the material of the insulting layer 3.

As explained above, micro through holes can be formed at any position byirradiating with an electron beam and introducing a reactive gas. Theprinciple of the technique of opening a through hole on a substrate byusing an electron and a reactive gas is known, see J. W. Coburn, J.Appl. Phys., Vol. 50, No. 5, pp. 3189-3196 (1979).

The feature of this method is that the physical damage of the target isvery small since electron bombardment is employed. Therefore by applyingthis technique to the nanocontact MR element, an etching of aninsulating layer can be performed by using an electron beam convergedinto a very fine beam without introducing a physical damage into theunderlying magnetic layer. Even in the case where the very small regionis locally etched, a degradation of the beam convergence due to a chargeup of the insulating layer can be prevented by coating it with ametallic film.

In the case of a nanocontact MR element, a good crystallinity at thenanocontact portion is required. Therefore, the electron beam etchingtechnique with the reactive gas is especially preferred. Besides, theprocess time is quite short since the range to be etched is verylimited. Further, after the etching process, the shape of the throughhole can be easily observed and process feedback can be made by theresult. These features of the electron beam process for the formation ofa nanocontact MR element are advantages.

In some case, after the micro through hole is formed in the insulatinglayer it may be necessary to take the work in process out into theatmosphere without forming the overlying magnetic layer, layered regionincluding the additive element or nonmagnetic intermediate (spacer)layer. In such a case, a surface of the underlying magnetic layerexposed at the bottom of the through hole may be undesirably oxidized byan atmosphere of a poor quality. In order to remove such an undesirablyformed oxide layer, the following two methods can be used.

The first method is to remove the oxide layer by using a conventionalsputter etching technique. In this case, however, damage may beintroduced into the magnetic layer. Therefore, after performing sputteretching of the oxide layer by using an ion beam, an annealing process ispreferably performed by using an electron beam or a laser beam in orderto improve crystal quality. The sputtering process, the annealingprocess and the following deposition process of the overlying layer arepreferably performed continuously without breaking the vacuum.

For the annealing process, conventional heating technique can beemployed as well.

The second method is to remove the undesirably formed oxide layer byirradiating with atomic hydrogen. This process may also be preferablyperformed continuously with the following deposition process of theoverlying layer without breaking the vacuum.

Atomic hydrogen can be generated by cracking a hydrogen gas. Forexample, hydrogen gas can be cracked (decomposed into a atomic hydrogen)by introducing the hydrogen gas into a filament made of tungsten or atube made of tantalum which is located near the work (specimen) andheated (for example in a temperature range of 1400 through 2000 degreesin centigrade or even higher). The distance between the nozzle and thework may be about 10 cm or larger.

In this case, an annealing process to improve the crystallinity of themagnetic layer may also be preferably performed at the same time orafter the reduction of the oxide layer is performed. A thermal radiationfrom the hydrogen cracking source, electron beam irradiation or laserbeam irradiation may be used in the annealing technique.

The above-mentioned process of removing the oxide layer can be employedin any other embodiment of the invention.

Twelfth Example

As the twelfth example of the invention, a process for making the microthrough hole by locally heating spots of the MR multi-layered film withEB will be explained FIGS. 34A through 34C are cross-sectional viewsshowing the manufacturing process of a magnetoresistance effect elementtaken as this example.

First, as shown in FIG. 34A, a PtMn anti-ferromagnetic layer 6 (14 nmthick), CoFe magnetic layer 1 as the pinned layer (2 nm thick), SiO₂insulating layer 3 (2 nm thick), CoFe layer as the free layer (2 nmthick) and Ta layer as the protective layer 9 (5 nm thick) are formedsequentially from the bottom to the top.

Next, as shown in FIG. 34B, an electron beam concentrated to a spotdiameter not larger than 10 nm is irradiated from above the Taprotective layer 9.

As a result, as shown in FIG. 34C, temperature rapidly rises in theregion irradiated with the electron beam, and invites enlargement of thegrain size, which causes segregation of Si atoms and O atoms forming theSiO₂ layer 3 along the interface or incorporation of a part thereof intothe CoFe layers 1, 2. As a result, the insulating layer 3 locallydisappears from portions irradiated with electron beams. Thus the upperand lower magnetic layers 1, 2 can be connected to each other by pointcontacts.

The structure shown in FIG. 35A is also employable, in which anonmagnetic spacer layer 4A of Cr, for example, and a nonmagnetic spacerlayer 4B of chromium oxide, which is an oxidized surface portion of thenonmagnetic spacer layer 4A, are inserted between the upper and lowermagnetic layers 1, 2.

Here again, in the same manner, by local EB irradiation from above theTa protective layer 9, as shown in FIG. 35B, local removal of the spacerlayers 4A, 4B and connection of the upper and lower magnetic layers 1, 2can be accomplished as shown in FIG. 35C. In this case, once theelectric conduction is attained between the upper and lower magneticlayers 1, 2 via the micro through hole formed in the nonmagnetic spacerlayers 4A, 4B, both advantages are accomplished, namely, an increase ofMR by point contact and an increase of sensitivity by the free layer 2being sensitive even to a low level signal magnetic field.

One of advantages of irradiation of an electron beam from above the Taprotective layer 9 is to omit the process of making the micro throughhole during deposition of the MR film, which contributes to creatingcleaner interfaces between stacked layers, and another advantage is toform point contacts by only one-shot EB irradiation, which contributesto shortening the process time.

This EB irradiation process is still effective even in the model shownin FIGS. 36A through 36C in which an oxide layer 1A (Co—Fe—O) byoxidization of the pinned magnetic layer 1 lies on the lower pinnedmagnetic layer 1, and in the model shown in FIGS. 37A through 37C inwhich an oxide layer 2A (Co—Fe—O) is formed under the upper freemagnetic layer 2.

In the case that electron beams are irradiated with a spot as shown inFIG. 38A, it sometimes results in forming a point contact PC at the veryposition irradiated as shown in FIG. 38C, or it sometimes results informing a plurality of point contacts PC around the irradiated spot asshown in FIG. 38B. In any of these cases, the point contacts can be usedas nanocontacts of magnetoresistance effect elements.

In the case that the magnetoresistance effect element is used in amagnetic head, the electron beam is preferably irradiated proximately tothe medium traveling plane.

FIG. 39 is a schematic diagram illustrating that EB irradiation positionis set nearer to the medium traveling plane than the device center C byreading alignment marks AM after the MR multi-layered film is formed.

FIG. 40 is a schematic diagram that illustrates configuration of adevice. The magnetoresistive film MR is sandwiched by upper and lowerelectrodes EL, and by vertical bias films HM from right and left sides.As shown here, the point contact PC formed by EB irradiation is out of acenter C of the device toward the medium traveling plane ABS. In thismanner, it is possible to locate the magnetic detector portion of the MRelement closer to the medium traveling plane ABS and thereby supply thesense current concentrically to the portion where a large signalmagnetic field is obtained from the recording medium.

Also, when etching is carried out by using EB as explained inconjunction with the eleventh example, a position nearer to the mediumtraveling plane ABS is preferably selected to form the micro throughhole.

In the instant example, in the region irradiated by EB, the crystalgrain size is increased, and crystalline defects are decreased. As aresult, the device resistance is decreased, and an enhancement of the MRchange was observed. However, improvement of the soft magnetism couldnot be confirmed clearly. The reason probably lies in that theelectrical nature of the element depends on the crystallographicproperty exclusively of the conductive region; however, in regard to thesoft-magnetic nature, since the free layer 2 entirely gets into exchangecoupling to move in magnetization as a through hole, the effect of thelocal decrease of defects does not appear clearly.

This demonstrates that local annealing by EB irradiation is a methodcapable of controlling the electrical nature and the magnetic nature ofthe element independently as compared with other methods heating theentire element in an oven, for example.

For example, FeCo of a bcc crystal structure exhibiting large crystalmagnetic anisotropy is expected to provide large MR, but its softmagnetism deteriorates as the crystal size increases. Taking it intoconsideration, as shown in FIG. 41A, bcc-FeCo substantially entirelymade up of minute crystal is formed, and EB is irradiated exclusively toits conductive region. Then, as shown in FIG. 41B, although the crystalsize slightly increases in the EB-irradiated portion, crystallinedefects decrease in the sense current conductive region. Thus, theelement satisfies both a large MR and soft magnetism. This method iseffective also when stacking a NiFe (Permalloy) alloy film to assist thesoft magnetism.

Annealing by EB irradiation can be used to promote selective growth onlyin a specific crystalline orientation.

FIG. 42 is a schematic diagram illustrating an example of the MR elementhaving particular growth axes (for example, [111], [100] and [110]).These growth axes can be confirmed as difference in contrast, forexample, in a SI (secondary ion) image obtained by irradiation with ionbeams. In case the MR element is made up of a plurality of crystalgrains different in surface orientation, noise may be produced duringoperation of the magnetoresistance effect element. This phenomenonbecomes more and more noticeable as the element is downsized to becomposed of a few number of crystal grains. Additionally, if the pointcontact is formed near a grain boundary, influences of the currentmagnetic field additionally affect the operation reliability.

Therefore, in the case of point irradiation of EB, the position forirradiation is preferably selected, to avoid such grain boundaries.Thus, by avoiding grain boundaries and by scanning with EB under specialcontrol, crystal grains of a specific orientation can be grown.

For example, as shown in FIG. 43A, if the EB irradiation spot isgradually expanded in a portion of [111]-oriented crystal grains, thenthe [111]-oriented portion can be enlarged. Then, it is desirable thatthe entire region of the point contact PC is uniform in orientation asshown in FIG. 43B.

In this example, improvement of the crystallographic property by EBheating may be carried out in an occasion during deposition of layers ofthe MR film instead of an occasion after deposition of all these layers.

FIG. 44A shows a model in which a contact through hole HC is formed in amulti-layered structure including a free magnetic layer 1, CrAs layer410 for the purpose of increasing the resistance change, SiO₂ layer 3,and Nb conductive layer 40 in the order from the nearest to thesubstrate (not shown). EB is irradiated into the contact through hole CHto heat the CrAs layer. This contributes to improving thecrystallographic property and orientation of the part of the CrAs layer410R and obtaining a structure exhibiting a high electron polarizingproperty.

After that, as shown in FIG. 44B, the magnetic layer as the pinnedlayer, anti-ferromagnetic layer 6 and protective layer 9 are formed. EBirradiation inserted in the midst of the stacking process can be used toheat only a specific layer.

On the other hand, as shown in FIG. 45A, local EB irradiation may becarried after all the layers of the MR film (sequentially from thebottom, CoFe free layer 1, CrAs layer 410, Cr spacer layer 4A, Cr oxidelayer 4B, CoFe pinned layer 2, PtMn anti-ferromagnetic layer 6 and Taprotective layer) are formed. In this case, both the formation of thenanocontact and improvement of the crystallographic property of theirradiated part of the CrAs layer 410R can be achieved.

That is, the atomic arrangement of CrAs layer 410 is reconstructed inaccordance with the atomic arrangement of underlying and overlyinglayers. Thus, by irradiating with EB locally onto the nanocontactregion, the selective annealing thereof may be effectively performedwithout affecting the remaining portion.

Additionally, crystalline defects, distortion or other damage introducedinto the underlying magnetic layer in the boring process of theinsulating layer 3 can be removed by EB irradiation.

FIG. 46A shows a structure having damage DM introduced in a top surfaceportion of the underlying magnetic layer 1 due to the boring process byRIE. If EB is irradiated into the through hole as shown in FIG. 46B, thedamage DM can be removed by local annealing (FIG. 46C).

As an alternative process, even when the upper magnetic layer 2 isformed to bury the hole and the buried portion is thereafter annealed byEB, the same effect is obtained, and simultaneously, crystalline defectsof the magnetic material buried in the through hole can be reduced aswell. As a result, a MR element having a high MR change can be obtained.

As explained above, local heating by irradiation of EB is advantageousfor the formation of nanocontact MR element because the requiredelectrical characteristics of the magnetic nanocontact and the requiredthrough hole magnetic characteristics of the free layer can be bothrealized.

The local heating may be performed by using a laser irradiation insteadof the electron beam irradiation. In the case of laser irradiation, ifthe surface layer is transparent to the laser beam, it becomes easy tofocus the beam onto the underlying portion.

For example, an insulating layer is formed after forming the free layer(or pinned layer), then the insulating layer is irradiated with a laserbeam to make a “pillar” which connects the underlying and overlyingmagnetic layers. Then, a pinned layer (or free layer) is formed on theinsulating layer. Thus a nanocontact MR element is formed.

Thirteenth Example

As the thirteenth example of the invention, a method of formingnanocontacts by FIB (focused ion beam) will be explained. In case ofFIB, because of a large mass of colliding particles (ions), irradiationonly is basically sufficient for etching.

FIGS. 47A and 47B are cross-sectional views illustrating a method ofmaking micro through holes in the SiO₂ layer 3 formed on the CoFemagnetic layer 1.

First, a PtMn anti-ferromagnetic layer (15 nm thick), not shown, isformed on a base layer (5 nm thick Ta), not shown. Thereafter, the CoFelayer 1 is formed thereon as the pinned layer of the MR element, and a 3nm thick SiO₂ layer 3 on the CoFe layer 1.

After that, as shown in FIG. 47A, FIB concentrated to a beam diameternot larger than 10 nm is irradiated onto a spot of the surface of theSiO₂ layer 3. If the dose of FIB is adequately controlled, the microthrough hole A will be formed in the SiO₂ layer 3 as shown in FIG. 47B.Ga ions typically used as the FIB source are liable to undesirably etchthe CoFe layer 1 as well, and need strict control of the dose thereof.If the etching selectivity of the SiO₂ layer 3 and the CoFe layer 1 issufficiently large, the CoFe magnetic layer can be prevented fromover-etching.

Selectivity can be raised by, for example, carrying out FIB processingwhile blowing a Freon-family gas as the reaction assist gas AG onto theregion to be processed, as shown in FIG. 48A. It will result inpreventing over-etching of the CoFe magnetic layer 1 and successfullyforming the micro through hole A as shown in FIG. 48B. In addition toFreon-family gases such as CHF₃, iodine gas is also usable.

Even when FIB is used to process the SiO₂ layer 3 as shown in FIG. 49A,FIB processing of the SiO₂ layer may be interrupted at a half depth ofthe SiO₂ layer 3 as shown in FIG. 49B, and the remainder may be etchedby using another method.

As this etching method, RIE or CDE having a very slow etching rate forthe magnetic layer 1 is preferably used to prevent undesirable problemssuch as over-etching of the CoFe magnetic layer 1 and damage causingdeterioration of the crystalline property (FIG. 49C). That is, byinterrupting FIB halfway and finally etching the magnetic layer 1 by RIEor CDE giving less damage thereto, etching with still less damage can beachieved.

In this case, the initial thickness of the SiO₂ layer 3 should bedetermined slightly larger than the thickness etched by RIE or CDE.

A Ta film, for example, may be formed on the top surface of the SiO₂layer 3 as shown in FIGS. 50A through 50C to minimize over-etching ofthe SiO₂ layer 3 by RIE or CDE. More specifically, as shown in FIG. 50A,a 3 nm thick Ta film 9 is formed on the SiO₂ layer 3, and its boringprocessing is carried out by FIB.

When the through hole reaches the top surface of the SiO₂ layer 3 asshown in FIG. 50B, the process is switched to RIE or CDE as shown inFIG. 50C.

By forming on the SiO₂ layer 3 a mask layer 9 of a material for whichlarge etching selectivity is obtained by RIE or CDE, it is possible tominimize a decrease of the film thickness by RIE or CDE with Freon gassuch as CHF₃ and to minimize unevenness of the thickness of the SiO₂layer 3 caused by excessive etching time or uneven progress of etchingalong the surface.

In order to taper the wide wall of the micro through hole such that amagnetic layer 2 minimized in defect can be buried, RIBE with obliqueangle of incidence is also preferable.

If a metal mask layer 9 is used, undesirable enlargement of the beamsize by charge-up can be prevented similarly to the case using EB.Additionally, the metal mask layer 9 functions as a buffer layer of themagnetic layer 2 formed thereon, and contributes to improving thecrystalline property of the magnetic layer 2 and thereby enhancing theoutput and sensitivity.

The process can be similarly carried out solely by FIB.

First as shown in FIG. 51A, after forming a multi-layered structurestacking the CoFe magnetic layer 1, SiO₂ oxide layer 3 and Ta mask layer9 from the bottom, FIB is irradiated.

Once the through hole is formed in the Ta mask layer 9 as shown in FIG.51B, the SiO₂ layer 3 is excavated by FIB again, as shown in FIG. 51C.At that time, assist gas AG, such as CHF₃ is introduced to increase theetching rate of the SiO₂ layer 3 and thereby increase the selectivity ofthe etching rate of the SiO₂ layer 3 relative to the CoFe magnetic layer1.

To simplify the process, the assist gas AG may be blown starting withthe first etching of the Ta film (FIG. 51A). However, in the case thatthe material used as the mask layer 9 acts on the assist gas AG, etchingmay undesirably progress even at the skirts of the FIB beam whereetching does not progress usually, and it may result in excessivelyenlarging the through hole. Therefore, it is desirable to select anassist gas AG that acts on the insulating layer 3 but does not act onthe mask layer 9 and the magnetic layer 1.

Furthermore, a spacer layer 4 (for example of Cu) may be inserted asshown in FIG. 52 to be used as an etching stopper.

In the above-mentioned explanation, gallium (Ga) is used as the ionsource, however, any other appropriate element can be used in theinvention. For example, if the gallium may possibly remain on theprocessed surface, argon (Ar) can be used as the ion source.

Fourteenth Example

As the fourteenth example, a process capable of forming micro throughholes simultaneously all over the wafer will be explained.Simultaneously forming micro through holes throughout the entire waferis more advantageous for shortening the process time than forming themone by one.

FIGS. 53A through 54D are diagrams showing the process taken as theinstant example.

First referring to FIG. 53A, a 0.1 .mu.m thick photo resist PR is coatedon an alumina insulating layer 3 (6 nm thick) formed on the magneticlayer (not shown), and it is patterned to the position X for the throughhole.

As shown in FIG. 53B, a 7 nm thick SiO₂ film 420 is formed thereon. TheSiO₂ film 420 coated the sidewall of the photo resist PR by thethickness of 5 nm. Further, as shown in FIG. 53C, a 0.1 .mu.m thickphoto resist PR is coated.

Then the surface is shaved to a thickness around 30 nm by ion milling orRIE etch-back to expose the SiO₂ 420 on the sidewall of photo resist PRon the top surface as shown in FIG. 53D such that a 5 nm thick line ofthe SiO₂ film 420 appear on the top surface.

This 5 nm thick line of SiO₂ layer 420 is next selectively etched by RIEusing CHF₃ gas as shown in FIG. 54A. Additionally, RIE using CHF₃—CF₄mixed gas is conducted to remove a half depth (approximately 3 nm) ofthe alumina insulating layer 3.

Then the pair of photo resist layers PR remaining on the top surface areremoved by RIE using O₂ gas, and the underlying SiO₂ film 420 is alsoremoved by RIE using CHF₃ gas. Since the etching rate of RIE using anyof these gases for the alumina insulating layer 3 is one fourth inmaximum, removal of the alumina insulating layer 3 by the etching isquite a little, if any.

Through the process explained above, 5 nm wide, 3 nm deep grooves G areformed by repeating the process shown in FIGS. 53A through 54B whilerotating the patterning direction by 90 degrees. Then, as shown in FIG.54D, a 5×5 nm square through hole CH is formed at the crossing point ofthese orthogonal grooves G.

This process explained above greatly reduces the time required forboring. When RIE is employed, the sidewall of the through hole CH isshaped to be as steep as 80 degrees or more. When CDE is employed, thesidewall of the through hole CH gently inclines the form of a wine cup.If the magnetic film buried thereon is the free layer, a gently inclinedsidewall ensures better soft-magnetism of the magnetic material buriedin the through hole.

Fifteenth Example

As the fifteenth example of the invention, a method of boring a throughhole using a needling technique by AFM (atomic force microprobe).

FIG. 55 is a schematic diagram for explaining a process using reducingreaction in this example.

A sample was prepared by forming an alumina insulating layer 3 (5 nmthick) on a magnetic layer 1. The needle of AFM is coated with a metalfilm, and an electric field is applied between the needle ND and thesample in a reducing atmosphere by blowing H₂-mixed forming gas toprevent generation of new oxides. As a result, a current suddenly beginsto flow at a certain magnitude of the electric field, and due to areducing reaction, the region stabbed with the needle ND becomes aconductive region (Al). Since the needle ND contacts, the electric fluxline is dense at the contact portion, and the reducing reactionprogresses from that portion.

A spacer layer 4 may be interposed between the alumina insulating layer3 and the magnetic layer 1. In case a metal oxide is used as thematerial of the insulating layer 3, such an oxide may be formed by firstforming a film of aluminum (Al) or other metal and thereafter oxidizingit.

The insulating layer 3 used in this example is preferably a metal oxide.However, in the case where SiO₂ is used, it is reduced with electricityfrom the needle ND to form Si or Si compound, and thereafter, as shownin FIG. 56, it is removed by RIE to complete the contact through holeCH.

Such processing may be carried out after the magnetic layer 2 is stackedon the insulating layer 3. That is, as shown in FIG. 57, if an electricfield is locally applied from the needle ND to a sample of a sandwichstructure of the magnetic layer 1, insulating layer 3 and magnetic layer2, the insulating layer 3 is locally reduced. Thus a local conductiveregion can be formed.

In an embodiment of the invention, an oxidation reaction is also usable.

FIGS. 58A through 58C are schematic diagrams for explaining a processusing oxidation.

On the magnetic layer 1, a layer 3A of silicon (Si), for example, isformed beforehand. When the needle ND is brought into contact therewithand an electric field in the opposite direction is applied in anoxidizing atmosphere, anodic oxidation locally progresses. As a result,as shown in FIG. 58A, a minute SiO₂ region is formed.

After that, this SiO₂ region is selectively removed by etching such asRIE. This etching is preferably conducted under a condition with largeetching selectivity relative to silicon (Si) as the matrix.

After that, the silicon layer 3A is oxidized into SiO₂. Thus theinsulating layer having the micro through hole is obtained.

The process using AFM technique is advantageous to confirm the positionfor the opening on the sample beforehand and facilitate its adjustment,if necessary. Especially when the MR element according to an embodimentof the invention is formed, because of its locally conductiveconfiguration, the conductive region is desired to be determined toavoid defects, foreign matter and boundaries. In such cases, bypreviously knowing the film surface morphology by AFM scanning, theboring position can be adjusted. Furthermore, when the needle ND made ofa magnetic material is used, this process has a great advantage in alsoenabling confirmation of the magnetic state of the sample surface by MFM(magnetic force microscope) technique.

Sixteenth Example

As the sixteenth example, the functions of the spacer layer 4 made of anonmagnetic material will be explained.

FIG. 59A shows a structure including a Cu layer (2 nm thick), forexample, first formed as a spacer layer 4 on the SiO₂ insulating layer 3overlying the CoFe layer 1 and defining the contact through hole CH, anda CoFe magnetic layer 2 (4 nm thick) thereafter formed thereon. Sincethis structure does not bring the magnetic layers 1 and 2 into directcontact, it can prevent degradation of the soft magnetism caused byexchange coupling of the free layer (for example, magnetic layer 2) withthe pinned layer (for example, magnetic layer 1).

However, the magnetic material buried in the contact through hole CHcontains a number of defects, and makes it difficult to quickly rotatemagnetization of the pinned layer and the free layer. To lessen thenumber of defects, the nonmagnetic layer 4 is first formed and the uppermagnetic layer 2 is next, as shown in FIG. 59A. This process permits theside surface of the contact through hole CH to be covered with the metalbuffer layer and the crystallinity of the magnetic material buried inthe contact through hole CH is improved. As a result, the magneticmaterial in the through hole CH can magnetically rotate together withthe magnetic layer around it and contributes to generating MR changessensitive to the signal magnetic field.

Also when the magnetic layer appearing at the bottom of the through holeCH is shaved by sputtering etching in the process of boring the throughhole CH or before the process of burying a film, the same bufferingeffect is ensured by forming the spacer layer 4 on the lower magneticlayer 1 as shown in FIG. 59B. After the through hole is opened, theupper spacer layer 4 and the upper magnetic layer 2 can be stacked asshown in FIG. 59C.

If the insulating layer 3 is etched by RIE using a Freon-family gas, acarbon film CF may be deposited on the bottom of the through hole CH(i.e. on the top surface of the lower magnetic layer 1) as shown in FIG.60A under certain etching conditions. This carbon film CF also functionsas a spacer layer 4, and the same buffering effect is obtained in thestacked structure as shown in FIG. 60B.

The through hole inside surface of the contact through hole CH is notnecessarily covered by the spacer layer 4. For example, the copperspacer layer 4 may have pin holes or may have a mesh-like structure inthe contact through hole CH. The lack of the spacer layer 4 limits themagnetic contact area.

Seventeenth Example

As the seventeenth example, a process for burying the contact throughhole with a magnetic material by plating will be explained.

If plating is used to bury the contact through hole with a magneticlayer, growth of the magnetic layer starts from the bottom of thethrough hole. Therefore defects can be decreased significantly.

For example, as shown in FIG. 61A, a SiO₂ insulating layer 3 is formedon the lower magnetic layer 1, and the contact through hole CH is formedthereafter. Subsequently, an electrode is connected to the magneticlayer 1, and the structure is immersed in a plating bath PL. If thestructure is immersed in a NiFe plating bath PL, growth starts from thetop surface of CoFe as the magnetic layer 1 exposed on the bottom of thecontact through hole CH. In this case, a Cu spacer layer 4 (not shown)may be stacked beforehand on the top surface of the CoFe magnetic layer1.

The NiFe layer 2 having grown from the bottom of the contact throughhole spreads out spherically just exiting the through hole CH, andstarts rapidly enlarging its surface area. Therefore, under a constantplating current, the growth speed decelerates. As such, when plating isused for an extremely minute contact through hole, the timing of platingfor burying the through hole can be controlled by appropriate adjustmentof the plating time. As such, the magnetic film formed in the contactthrough hole by plating has less defects, and expresses a large MR.

Then, the antiferromagnetic layer 6 is formed and the magnetization ofthe ferromagnetic layer 2 is fixed in one direction by theantiferromagnetic layer 6. According to the embodiment, it becomespossible to control the magnetic domain of the ferromagnetic layer 2 bystacking the antiferromagnetic layer after burying the contact throughhole CH by a plating technique. As a result, a MR element with a lownoise can be realized and one problem of the aforementioned prior art(M. Munoz (Applied Physics Letters vol. 79, No. 18, pp 2946-2948 (2001))can be solved

Eighteenth Example

As the eighteenth example of the invention, a method of fabricating a MRelement having a nanocontact will be explained, in which the electricalflow direction is parallel to the film plane.

FIG. 62 is a schematic diagram that shows the configuration of the MRelement taken as this example. That is, halfway of the electric currentfrom the first electrode EL1 to the second electrode EL2, the pinnedlayer 1, current-confining (A-B) region PC and free layer 2 are located.In this example, the signal magnetic field SM enters in the free layer 2from the part of the second electrode EL2.

FIGS. 63A through 63D are diagrams illustrating a process of fabricatingsuch a MR element.

First, as shown in FIG. 63A, a CoFe magnetic layer (5 nm thick) FM isformed, and a PtMn anti-ferromagnetic layer 6 (15 nm thick) is formedthereon. Further, photo resist PR is formed patterned thereon such thatits edge (end) resides on the position for confining the current.

Next, as shown in FIG. 63B, part of the PtMn layer 6 overlying the CoFelayer FM to be used as the free layer is removed by ion milling.

Next, as shown in FIG. 63C, trimming is carried out by beam scanning byFIB along the edge of the photo resist PR to form the current-throttlingportion PC, As a result of the processing, the configuration as shown inFIG. 63D is obtained. Thereafter, the first and second electrodes EL1,EL″ are formed.

However, on the sectional surface of the free layer 2 taken along theA-B line of FIG. 63D, the upper perimeter of the free layer 2 isundesirably rounded as shown in FIG. 64 due to influences of the FIBbeam profile, and this makes it difficult to control the resistancevalue. However, this “rounding” of the magnetic layer FM can beprevented by using a protective film PF and carrying out the FIBprocessing from beyond the protective film PF. The protective film PF ispreferably a high-resistance film, like an insulating film, to dividethe current with the magnetic film.

FIG. 66 shows an aspect of an element processed from the state of FIG.63B by coating a photo resist to form a protective layer PR on the freelayer. In this example, the processing for making the current throttlingstructure by FIB is conducted from this state. It results in protectingsurfaces of the pinned layer 1 and the free layer 2 when they areprocessed by FIB etching, and therefore minimizes fluctuation ofresistance by “rounding”.

It is also possible to make out the current-throttling narrower than theprocessing width by making use of the implantation of gallium (Ga).

FIG. 67 is a schematic diagram that shows an aspect of an element inwhich Ga has been introduced into an end portion of the FIB-processingportion. In the Ga-introduced region IZ, crystals of the CeFe layers 1,2 are broken, and their resistance values rise. Thus the FIB processingresults in making a junction effectively narrowed by several to ten andseveral nm than the physical processing width from opposite sides. Thus,by implantation of FIB source particles, such as Ga, a substantiallynarrower contact than the physical processing width can be made.

MR characteristics can be even improved by irradiating thecurrent-throttling with an EB in order to anneal the crystal defectthereof.

While the present invention has been disclosed in terms of variousembodiments in order to facilitate a better understanding thereof, itshould be appreciated that the invention can be embodied in various wayswithout departing from the principle of the invention. Therefore, theinvention should be understood to include all possible embodiments andmodification to the shown embodiments which can be embodied withoutdeparting from the principle of the invention as set forth in theappended claims.

1. A magnetoresistance effect element comprising: a first ferromagneticlayer; an insulating layer overlying the first ferromagnetic layer; anda second ferromagnetic layer overlying the insulating layer, theinsulating layer having a through hole penetrating its thicknessdirection at its predetermined position, the first ferromagnetic layerand the second ferromagnetic layer being electrically connected to eachother via the through hole, an additive element which is different fromelements composing the first and second ferromagnetic layers beingincorporated at the connected portion between the first and secondferromagnetic layers, and a thickness of the connected portion where theadditive element is incorporated being not larger than 10 atomic layers.2. A magnetoresistance effect element according to claim 1, wherein anelectric resistance between the first ferromagnetic layer and the secondferromagnetic layer changes with a relative arrangement ofmagnetizations of the first and second ferromagnetic layers.
 3. Amagnetoresistance effect element according to claim 1, wherein thethrough hole converges toward the first ferromagnetic layer, and theconverged end of the through hole defines the opening width.
 4. Amagnetoresistance effect element according to claim 1, wherein theinsulating layer has a plurality of the through holes.
 5. Amagnetoresistance effect element according to claim 1, whereinresistance between the first ferromagnetic layer and the secondferromagnetic layer is in a range from 5Ω to 100 KΩ, and amagnetoresistance ratio of the magnetoresistance effect element is notsmaller than 20%.
 6. A magnetoresistance effect element according toclaim 1, wherein the insulating layer is a polymer, or an oxide, nitrideor fluoride containing at least one element selected from the groupconsisting of aluminum (Al), titanium (Ti), tantalum (Ta), cobalt (Co),nickel (Ni), silicon (Si), zirconium (Zr), hafnium (Hf) and iron (Fe),and the first and second ferromagnetic layers are made of iron (Fe),cobalt (Co), nickel (Ni), or made of an alloy, an oxide, a nitride or aHeusler alloy containing at least one element selected from the groupconsisting of iron (Fe), cobalt (Co), nickel (Ni), manganese (Mn) andchromium (Cr), or made of a compound semiconductor or an oxidesemiconductor including at least one element selected from the groupconsisting of iron (Fe), cobalt (Co), nickel (Ni), manganese (Mn) andchromium (Cr).
 7. A magnetoresistance effect element including aplurality of the magnetoresistance effect elements according to claim 1,wherein the magnetoresistance effect elements are formed in one body andelectrically connected in series.
 8. A magnetic reproducing elementcomprising a magnetoresistance effect element including: a firstferromagnetic layer; an insulating layer overlying the firstferromagnetic layer; and a second ferromagnetic layer overlying theinsulating layer, the insulating layer having a through hole penetratingits thickness direction at its predetermined position, the firstferromagnetic layer and the second ferromagnetic layer beingelectrically connected to each other via the through hole, an additiveelement which is different from elements composing the first and secondferromagnetic layers being incorporated at the connected portion betweenthe first and second ferromagnetic layers, and a thickness of theconnected portion where the additive element is incorporated being notlarger than 10 atomic layers, the magnetoresistance effect element beingprovided on a path of the magnetic flux emitted from a magneticrecording medium so that the first and second ferromagnetic layers areserially aligned on a path of the magnetic flux emitted from a magneticrecording medium, and the magnetoresistance effect element detecting adifference between magnetization directions of the first and secondferromagnetic layers as a resistance change.
 9. A magnetic reproducingelement according to claim 8, wherein one of the first and secondferromagnetic layers located remoter from the magnetic recording mediumis pinned in magnetization in one direction.
 10. A magnetic reproducingelement comprising a magnetoresistance effect element including: a firstferromagnetic layer; an insulating layer overlying the firstferromagnetic layer; and a second ferromagnetic layer overlying theinsulating layer, the insulating layer having a through hole penetratingits thickness direction at its predetermined position, the firstferromagnetic layer and the second ferromagnetic layer beingelectrically connected to each other via the through hole, an additiveelement which is different from elements composing the first and secondferromagnetic layers being incorporated at the connected portion betweenthe first and second ferromagnetic layers, and a thickness of theconnected portion where the additive element is incorporated being notlarger than 10 atomic layers, the magnetoresistance effect element beingarranged so as to make a main plane of the first ferromagnetic layerbeing substantially perpendicular to a recording surface of the magneticrecording medium.
 11. A magnetoresistance effect element according toclaim 10, wherein the through hole is out of a center of symmetry inmajor plane of the insulating layer toward then magnetic recordingmedium.